The covenant that God made with Abram is about the Savior and salvation. God would send into the world a Savior who would come forth from Abram, and in and through Him, the blessings of salvation would reach to all the families of the earth: the Savior would bring salvation to God's people. But exactly how would He do that? How exactly does God save His people? We talked about this in God's covenant with Noah, and we're going to see the same thing here that we saw with Noah: Salvation is by grace alone, through faith alone, in Christ alone.1 That's how God saves His people. It wasn't any different for Abraham than it is for us today. God's people in the Old Testament weren't saved in any other way than the way we're saved today. There's only one Savior and there's only one way of salvation, and that is by grace alone through faith alone in Christ alone.
A) God freely lavishes His favor on sinners by GRACE alone: Abraham was an object of God's favor all his life. But he never deserved any of it. That's what grace is. God dealt with Abraham in grace. Now, that doesn't mean that God never gave Abraham any commands to obey. In Genesis 17:1, for example, the Lord says to Abraham, “I am God Almighty; walk before Me, and be blameless.” God called Abraham to live a holy life; to be blameless; to walk before Him. God gave him commands. But God's favor towards Abraham was never based on Abraham keeping those commands. God's disposition towards him was never based on Abraham fulfilling certain conditions. We see this in the way that God made the promises to Abraham. God never came to him saying, “Abraham, IF you obey Me and live a holy life and walk blamelessly before Me, THEN I will confirm these promises to you.” Or: “If you CONTINUE to obey Me and live a holy life, I will CONTINUE to confirm My promises to you.” The promises God made to him were unconditional: “I will give [this land] to you and to your descendants forever” (13:15); “I will make your descendants as the dust of the earth” (13:16); “I will make you exceedingly fruitful, and I will make nations of you, and kings will come forth from you” (17:6). God simply made promises to Abraham; there were no conditions attached.
Even Abraham's sin couldn't nullify or revoke God's promises. Remember what happened in the last half of Genesis 12? Abraham had used his wife as a shield to protect himself. His behavior was so bad they had him deported (12:19-20). So, in his first test since entering Canaan, Abraham fell flat on his face. How does God respond? Does He revoke the promises He made back in Genesis 12? (Or at least threaten to revoke them if Abraham doesn't shape up?) No. Rather, God continues to reaffirm those promises to Abraham throughout the rest of his life (13:14-18; 15:1-21; 17:1-22; 22:15-19). Then, later, in Genesis 20, we find Abraham doing the same thing again: He leaves the land of Canaan, he introduces his wife as his sister, and once again, she ends up in a king's harem—probably for quite some time.2 When everything comes to light, Abraham is again severely rebuked by a pagan king (vv8-10). Now, this was anywhere from 15-25 years after the first time this had happened in Genesis 12. Abraham is a mature believer now. He knows better. But here in Genesis 20, we find him, yet again, relapsing back into his old sins. Well, how is God going to respond this time? The chapter headings say it all: “Genesis 20: Abraham's treachery. Genesis 21: Isaac is born.” In other words: God fulfills His promise to Abraham—not at the height of his obedient faith—but in the midst of the very worst of his sin and failure. That's how God responds to Abraham's sin. Are you amazed? You should be. This is the gospel. God's covenant mercies were never mediated by Abraham's obedience, nor could they ever be nullified by his sin. God's blessing didn't come to him apart from his sin—but in the midst of it. He would at times fail God, but God would never fail him.
Fact is, Abraham couldn't get away from God's mercies. No matter what he did; no matter how hard he seemed to try. At times he wandered away from the Lord; at times he fell flat on his face. But he could never get away from God's blessing or nullify the promises God made to him.3 Abraham had good days, and he had bad days, but God's blessing never went up and down based on his obedience. And it's the same for you if you belong to Christ. Your sin can never nullify God's promises to you, because God's promises to you were never conditional on your obedience to His commands. God's blessing doesn't stop when we stumble and fall—it continues and runs through even our worst failures. This is what the gospel is all about. God lavishes His blessing upon weak Christians who continue to fall flat on our faces. Like Abraham, we too will have good days, and we will have bad days: “But the lovingkindness of the Lord is from everlasting to everlasting on those who fear Him.” (Psalm 103:17).
B) God freely lavishes His favor on sinners through FAITH alone: How was it that Abraham was able to enter into these covenant mercies, and live out all of his days under the blessing and favor of God? We're given the answer in Genesis 15:6. We'll be looking at Genesis 15 in more detail later, but let's just look at this verse together now. The Lord had just promised in verses 4-5 that He would multiply Abraham's descendants like the stars of the heavens. We then read in verse 6: “Then he believed in the Lord; and He reckoned it to him as righteousness.” This is the first time in the Bible where faith is explicitly joined together with justification; it's the first time that we're told that the way justification happens is through faith.4 When and how was it that God credited righteousness to Abraham? When he believed God's Word—that's all he did.5 The truth in this single verse is so important that the New Testament quotes it four times. For instance, Paul says in Galatians 3:6-7: “Even so Abraham 'believed God, and it was reckoned to Him as righteousness.' Therefore, be sure that it is those who are of faith who are sons of Abraham.” (cf. Romans 4:3,22 and James 2:23). So, justification comes about through faith. We could note here a few things in particular about faith:
1) FAITH IS ALONE: Paul writes in Romans 4:3-5, saying: “For what does the Scripture say? 'Abraham believed God, and it was credited to him as righteousness.' Now to the one who works, his wage is not credited as a favor, but as what is due. But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness. . .” Paul here quotes from the passage in Genesis 15:6 and draws out one implication for us: Abraham was not justified by a combination of faith in Jesus plus his own obedience. Genesis tells us that Abraham was justified by faith, and Paul clarifies that he was justified by faith alone.6 Notice how Paul puts it. Paul doesn't say: “But to the one who does not ONLY work, but ALSO believes. . .” Rather, he puts them at a complete contrast: “But to the one who does NOT work, BUT believes. . .” In other words, Paul is not saying: “NOT ONLY works, BUT ALSO faith.” Rather, he's actually saying: “NOT ALSO works, BUT ONLY faith.” It's not just that we're justified by faith—Paul's point is that we're justified by faith alone.7
2) FAITH IS INSTRUMENTAL: Again, speaking of faith, Paul tells us in Romans 4:13, “For the promise to Abraham or to his descendants that he would be heir of the world was not through the Law, but through the righteousness of faith.” The Greek preposition that Paul chooses to use here has a very particular meaning attached to it:8 It's clear Paul is telling us that this promise given to Abraham was received through (or by) faith, as opposed to because of his faith or on the basis of his faith. This is the way that Paul consistently speaks: we're not justified on the basis of our faith; we're simply justified through faith. In other words, faith isn't meritorious; it's simply instrumental. Faith isn't why we're justified; it's simply how we're justified. Faith isn't the cause of our justification; it's simply the means. Abraham didn't achieve God's blessing because his faith was so great; he simply received the promise God was making to him, through simple faith in His Word. This is important, because sometimes it's almost as though we start trying to turn faith into another kind of work—something we must do, or attain to. But Scripture tells us that God's favor isn't something that can be achieved. Entering into God's covenant mercies isn't something that's even achieved by faith—rather, it's simply received by faith. God holds out His promises to us as a free gift. We simply open our hand and take them.9
3) FAITH CAN BE WEAK: As we read through the Genesis narrative, we see that Abraham's faith in God was constantly going up and down. At the beginning of Genesis 12, he has enough faith in the Lord to leave everything he knows behind, and take his family to the land where God was calling him. But by the end of the same chapter, he doesn't even have enough faith in God to be honest and tell the Egyptians that Sarah was his wife. In Genesis 15, the Lord promises to give Abraham a son, and we read in verse 6 that he believes in the Lord. But in the very next chapter, we see Abraham and Sarah struggling in faith, starting to think maybe they needed to help God out with His promise. And so, Abraham takes Sarah's maid Hagar as another wife, in order that God's promise of an offspring might be reckoned through her, because they couldn't believe at that point that God could really still give Abraham a son through Sarah. So, sometimes Abraham's faith seems unwavering; but other times it seems almost non-existent! Abraham was a man of faith—but even his faith was never a perfect faith. And this is so comforting for us. Isn't it good news that it's not the amount of our faith that brings us into God's favor, but the object of our faith. As one put it: “A little faith in the Lord Jesus saves.”10
C) God freely lavishes His favor on sinners in CHRIST alone: God's favor comes by grace alone through faith alone. But this faith is not just faith in God in general. God's favor comes through faith in Jesus Christ. Salvation only comes through the Savior. We can see this in a few different ways:
1) First, Jesus is the SEED that God promised. We saw this earlier. Jesus is the seed that God promised to Abraham—the seed through whom all the nations of the earth would be blessed. It's only in Christ, Abraham's true seed, that God's blessing flowed to Abraham himself and then would flow to all the nations. All the promises that God made to Abraham are only fulfilled in Christ.
2) Secondly, Jesus is the SAVIOR that Abraham trusted. We've seen that Abraham was a sinner—and yet God dealt with him in grace. But how could God do that? If Abraham was truly a guilty sinner, and if God is just and will by no means leave the guilty unpunished (Nahum 1:3), then how could God deal with Abraham in grace without compromising His justice? The answer is that the day was coming that Jesus would go to the cross to take all the punishment of all those who belong to Him—including Abraham.11 Abraham was a believer in Christ. That's why Jesus said to the Jews in John 8:56, “Your father Abraham rejoiced to see My day, and he saw it and was glad.” That's why we find Abraham building altars and offering up burnt offerings. He was acknowledging his sin and his need for atonement. The blood of bulls and goats could never take away his sin, but they pointed forward to the One who would. Abraham looked forward to the coming Savior, the lamb of God.12
3) Thirdly, Jesus is the SUBSTANCE that the narratives fore-pictured. Genesis doesn't just point us to Christ through the promises God was making. Throughout Genesis, we're also pointed to Christ through the various pictures Scripture was setting before us. In particular, Scripture sets forth both Abraham and Isaac, not only as believers in Christ, but as pictures of Christ, in the following ways:
A) ISAAC is set forth as a picture of Christ's SUFFERINGS: Genesis 22 tells the story of how God tested Abraham, asking him to offer up his son Isaac as a burnt offering. It is a remarkable testimony of Abraham's faith; that he was willing to give up to the Lord what was most precious to him in all the world. But this narrative also serves in many ways to point us forward to the cross: Just as it was with Isaac, Christ was God's beloved son; the son of promise; His “only” son (verse 2). And just like with Isaac, Jesus was given a load of wood to carry up a mountain; it was given to him by his father, and he was to be offered up upon it on the mountain (verse 6). Just like Isaac, who walked with his father and even submitted himself to being bound by his father on the mountain, so too Christ raised no objections to the plan and purpose of his father, but submitted himself entirely to Him, even to the point of death (verse 9). And Hebrews tells us that Abraham received Isaac back from the dead as a type of Christ's death and resurrection (verse 13; cf. Hebrews 11:19).13 It's significant that, at the end of the narrative, Abraham names that place, “The Lord Will Provide” (verse 14). Why not name it, “The Lord Did Provide”? Probably because Abraham himself understood that these events were ultimately looking forward to something else still yet to come.14 Later, we learn that this same place, Mount Moriah, was actually the very place the temple would be built. We read in 2 Chronicles 3:1, “Then Solomon began to build the house of the Lord in Jerusalem on Mount Moriah. . .” It would be here that God would provide sacrifices of atonement for the many sins and failures of His people. But, ultimately, even those offerings point us forward further still, to Christ. Abraham can tell us that the Lord will provide because he was looking forward to the promised Messiah—the One who would provide for His people in a way that his son and the ram only faintly fore-pictured. Abraham looked forward to the lamb of God who, through his sufferings, would take away the sin of the world.15
B) ABRAHAM is set forth as a picture of Christ's OBEDIENCE: Isaac isn't the only type of Christ in Genesis 22. Abraham is also set forth as a type of Christ—only in a different way. Isaac serves to picture Christ in his sufferings; Abraham serves to picture Christ and his obedience. We see this in Genesis 22:18, where, after Abraham had offered up the ram, the Lord declares to him: “In your seed all the nations of the earth shall be blessed, because you have obeyed My voice.” Earlier, we saw that Christ was the promised seed, through whom blessing would come to the nations. But we also see Christ here in another way. Towards the end of the verse, we're told that the nations would be blessed because of Abraham's obedience. What do we make of this? Scripture clearly tells us that Abraham inherited the promises by grace alone through faith alone—emphatically not on the basis of his obedience—indeed, the two are completely mutually exclusive systems (Romans 4:13-16; Galatians 3:16-18). So how are we to interpret these words? We interpret them the same way we did with Noah. Remember how the Lord had told Noah in Genesis 7:1 that his entire household was to enter the ark, but that they were only saved because he alone was righteous? Noah was a picture of Christ, in that his entire family was saved only because of and through and in union with him.16 So it is here with Abraham. Notice what God is saying: NOT: “Abraham, you will be blessed because you have obeyed My voice”; NOR: “the nations will be blessed because they will obey My voice”; BUT: “Abraham, the nations will be blessed because you have obeyed My voice.” This is not a personal, merited righteousness—but a covenantal, imputed righteousness. Scripture is giving us a glimpse of the truth that the nations would enter into God's blessing on the basis of the obedience of another. Here Abraham serves as a type of Christ: we (the nations) are blessed because he (Jesus) obeyed.17
The Lord's words to Abraham in Genesis 22:18
NOT: "Abraham, YOU will be blessed because you obeyed My voice”
NOR: “Abraham, the nations will be blessed because THEY will obey My voice”
BUT: “Abraham, the nations will be blessed because you obeyed My voice”
Don't we often begin to think that God blesses us as Christians when and as we obey Him and keep His commandments? Now, God wants us to obey Him and keep His commandments! And we'll talk more about that ahead. But isn't it freeing, isn't it wonderful to know that, actually, God blesses us, not on the basis of our obedience, but because of the obedience of another? The truth is, God's blessing flows to us because of Jesus. God continues every day to pour out His full blessing upon us in the midst of, and despite our many sins (by grace alone). What's more, He continues to pour out this blessing upon us completely apart from any of our Christian obedience (by faith alone). And He does so because Jesus paid your sin debt in full and His righteousness has now been credited to you (in Christ alone). God's blessing wasn't based on Abraham's spiritual achievements in the Christian life. It wasn't based on his obedience, or on his devotion, or even on his feelings. It wasn't based on him at all. And it's the same for us in Christ. God's favor is based on His promise to bless all those who belong to Jesus. We didn't earn God's favor at conversion. We don't earn it now by trying to be good Christians. We never deserved it in the first place, and we never will. But if you belong to Jesus, then God's favor is upon you, and just like Abraham, you won't be able to get away from it.
1 Anthony Burgess puts it this way in his work, The Vindication of the Law: “There are these three main concurrent causes to our justification: The grace of God as the efficient, Christ as the meritorious, and faith as the instrumental.” (Burgess, p23).
2 Genesis 20:17-18 hint at this. Abraham here prays for Abimelech, after which God again opens up the wombs of his wife and maids to bear children again (for the Lord had closed all their wombs from the time Sarah had been taken into the harem). Now, if the closing of the wombs of the women in the palace was noticeable, Sarah must have been there some time.
3 We could describe all this in just two words, the words recorded at the beginning of Genesis 20:3, after Abraham's grievous sin: “But God.” Abraham failed God again and again. But God never, ever failed to keep His promise to Abraham.
4 From Ligon Duncan course on Covenant Theology. Jonathan Edwards puts it this way: “[with Abraham] the great condition of the covenant of grace, which is faith, was now more fully made known” (A History of Redemption). With Noah, we're told later in Hebrews that he was made righteous by faith. But here with Abraham it is clear from Genesis itself (15:5-6). Another Old Testament passage that connects faith and justification is Habakkuk 2:4: “but the righteous shall live by faith.”
5 Someone may ask: Why is Scripture only now describing Abraham's justification? Wasn't Abraham already justified at this point? Calvin answers in his note on Genesis 15:6: “We must now notice the circumstance of time. . .by a consideration of the time in which this was said to Abram, we certainly gather. . .that holy men are only justified by faith, as long as they live in the world. If any one object, that Abram previously believed God, when he followed Him at His call, and committed himself to His direction and guardianship, the solution is ready; that we are not here told when Abram first began to be justified, or to believe in God; but that in this one place it is declared, or related, how he had been justified through his whole life. For if Moses had spoken thus immediately on Abram’s first vocation, the cavil of which I have spoken would have been more specious; namely, that the righteousness of faith was only initial (so to speak) and not perpetual. But now since after such great progress, he is still said to be justified by faith, it thence easily appears that the saints are justified freely even unto death. . .”
6 Paul makes this even more clear in Galatians 2:16, where he says: “nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, so that we may be justified by faith in Christ and not by the works of the Law; since by the works of the Law no flesh will be justified.” See also Romans 4:13. In the broader passage of Romans 4:1-15, we could also note that Paul shows that God's promise of salvation is to be received, in particular, through faith alone apart from works (vv1-8), apart from circumcision (vv9-12), and apart from the Law (vv13-15).
7 As Motyer puts it: “Abraham takes a second wife and has a child, Ishmael. . .But God simply disallows this device. He will not permit Abraham to contribute to the fulfilling of the divine promises. When Abraham does seem to make a contribution, when he and Sarah have a child by the ordinary processes which God has ordained, the narrative is very careful to tell us that he does so totally by the enabling of God. God fulfills his promises in his own time, in his own way, and by his own power. The covenant points to a salvation which is all of God; man is in no position to contribute or to co-operate.” (Covenant and Promise). This Scripture (Romans 4:3-5) speaks of speaks of God justifying “the ungodly” (v5) by faith. Here the unrighteous man, who even has no works to speak of, without and apart from any moral uprightness or religious deeds, simply believes in Jesus—and is justified. It is a slightly different truth in Galatians 3:11, where Paul quotes from Habakkuk 2:4 (see also Romans 1:17). Here, Paul tells us: “Now that no one is justified by the Law before God is evident; for, 'the righteous man shall live by faith.'” In Romans 4, it's an ungodly man who is justified by faith, but here in Galatians 3:11, it's actually “the righteous man” who is also justified by faith. What is the significance? It is a beautiful truth: We enter into God's favor at the beginning by faith alone, completely apart from works. But it's also true that even a mature Christian man who has learned to walk with the Lord and has begun, out of love for Christ and a desire for his glory, to engage in good works—yet still, even that man always and forever continues to be justified not by those works—but only through faith in Christ; for even the righteous man shall still be justified by faith. So, faith alone isn't just what justifies us at the beginning; faith alone is what continues to justify us till our dying breath. Anthony Burgess has some wonderful sayings on this point as well in his Vindication of the Law. He says: “Take notice of this, that justification by works does not only exclude the works of the Law, but all works of the gospel, yea, and the works of grace also.” (p21). Again: “we know, that the Apostle excludes the works of David and Abraham, that they did in obedience to the Law, to which they were enabled by grace; so necessary is it in matter of justification and pardon to exclude all works, anything that is ours. . .” (pp233-34). And lastly: “Why is that doctrine of making Angels and Saints mediators and intercessors so odious, but because it joins Christ and others together in that great work? Do you not [do] the like, when you join your love and grace with Christ's obedience? . . . Idolatry make[s] the works of Christ, a Christ.” (pp25-26).
8 This Greek preposition (Gr. dia) can be used in two different ways, which in turn, give it two different meanings. When it's used in the accusative tense, it takes on the meaning of “on account of,” or “because of”; whereas when it's used in the genitive tense, it takes on the meaning of “through,” or “by means of.” Paul consistently uses dia in the genitive when speaking of faith.
9 Colquhoun puts it this way: “It is one thing, to be justified by faith, merely as an instrument by which, a man receives the righteousness of Christ; and another, to be justified for faith, as an act or work of the law. If a sinner, then, rely on his actings of faith, or works of obedience to any of the commands of the law, for a title to eternal life; he seeks to be justified by the works of the law, as really as if his works were perfect. If he depend, either in whole or in part, on his faith and repentance, for a right to any promised blessing; he thereby, so annexes that promise to the commands to believe and repent, as to form them for himself, into a covenant of works.” (Treatise of the Law and Gospel, p25). And again he says: “All indeed who, according to the covenant of grace, attain justification, are justified by faith; but, it is one thing to be justified by faith, as merely the instrument of justification; and another, to be justified for faith, as an act, or work, affording a title to justification. It is one thing, for faith as an act of obedience, and as being seminally all sincere obedience, to give a title to justification; and a very different thing, for faith as a mean[s] or instrument, to receive a title to it. Faith, according to the gospel, gives no manner of title, to the smallest blessing of the everlasting covenant; but it receives the surety-righteousness of the second Adam, which gives a full title to every one of them.” Burgess likewise says: “Now to set up works is to oppose faith, as the Apostle argues; therefore faith, as it is a work, is to be opposed to itself, as it is an instrument justifying.” (p24). And again, Burgess writes: “[Justification] is not, because of the dignity of faith, but by Christ. You see the hyssop (or whatever it was) which did sprinkle the blood, was a contemptible herb, yet the instrument to represent great deliverance.” (Vindication of the Law, p28).
10 Watson speaks of this in his Body of Divinity: “We must distinguish between weakness of faith and no faith. A weak faith is true. The bruised reed is but weak, yet it is such as Christ will not break. Though thy faith be weak, be not discouraged. 1) A weak faith may receive a strong Christ. A weak hand can tie the knot in marriage as well as a strong one; and a weak eye might have seen the brazen serpent. The woman in the gospel did but touch Christ’s garment, and received virtue from him. It was the touch of faith. 2) The promise is not made to strong faith, but to true. The promise says not whosoever has a giant-faith, that can remove mountains, that can stop the mouths of lions, shall be saved; but whosoever believes, be his faith ever so small. Though Christ sometimes chides a weak faith, yet that it may not be discouraged, he makes it a promise. . . (Matt. 5:5). 3) A weak faith may be fruitful. Weakest things multiply most; the vine is a weak plant, but it is fruitful. Weak Christians may have strong affections. How strong is the first love, which is after the first planting of faith! 4) Weak faith may be growing. Seeds spring up by degrees; first the blade, then the ear, then the full corn in the ear. Therefore, be not discouraged. God who would have us receive them that are weak in faith, will not himself refuse them. Rom. 14:4: A weak believer is a member of Christ; and though Christ will cut off rotten members from his body, he will not cut off weak members.” (Watson, p220).
11 This is exactly what Paul is saying in Romans 3:23-26: “for all have sinned and fall short of the glory of God, being justified as a gift by His grace through the redemption which is in Christ Jesus; whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed, for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus.” Paul is explaining how it is that God could pass over the sins of Old Testament believers and yet not compromise His justice: He didn't sweep their sins under the rug and pretend they weren't so bad. God dealt in full with Abraham's sin; it's just that instead of punishing Abraham for his sin, God punished His own Son in his place.
12 Francis Roberts draws this truth out from the Scripture we've been looking at, Genesis 15:6. He writes: “Abraham the father of all believers was justified; not by a general faith, assenting to God's Word as true in general, but by a particular faith. . .He believed in the Lord; which here notes, not only assent, but also particular application of it to himself by affiance, trust, confidence, recumbency, etc, in the Lord. And therefore it was imputed to him for righteousness.” (Roberts, p579).
13 Bruce Waltke describes the narrative in Genesis 22 in this way: “Within the canon of Scripture, the story of Abraham's willingness to obediently sacrifice his son of promise typifies Christ's sacrifice. Abraham's declaration that 'God himself will provide the lamb' (22:8) resonates with God's offer of the Lamb to save the world. . .Like Isaac, Christ is a lamb led to the slaughter, yet he does not open his mouth. Just as Isaac carries his own wood for the alter up the steep mount, Christ carries his own wooden cross toward Golgotha (see John 19:17). Just as Abraham sacrificially and obediently lays Isaac on the altar (Gen. 22:9), so Christ sacrificially and obediently submits to his father's will. . .Symbolically, Abraham receives Isaac back from death, which typifies Christ's resurrection from the death of the cross (Heb. 11:19).” (Waltke, Genesis, pp210-11).
14 This insight about the future tense of v14 and its implications was gratefully gleaned from Tim Cain (Kaleo Church, CA).
15 Isaac is an eminent type of Christ in other ways as well. We see Christ, also, in the birth of Isaac, when we consider that: 1) the birth of Isaac came about as the direct fulfillment of God's promise (as with Christ); 2) the birth of Isaac only took place after much waiting and longing for the promise (as with Christ); 3) the birth of Isaac took place at the precise appointed time God had set (18:14; 21:12; as with Christ, cf. Galatians 4:4); 4) the birth of Isaac was miraculous (as with the virgin birth); 5) and the birth of Isaac brought great joy to some (IE, Sarah) but distress to others (IE, Hagar and Ishmael who are then cast out; as it was with Christ, cf. Luke 2:34). We also see Christ in the marriage of Isaac recorded in Genesis 24. Here the father (Abraham) commissions his servant with the great task of bringing home a bride for his son (Isaac). And this is a beautiful picture of our mission as God's people: God the Father has thus commissioned His servants with the great task of bringing home a bride for His Son, Jesus—this is what our mission is—to bring home the bride of Christ from among the nations.
16 Noah served both to show us how God deals with believers (on the basis of grace alone) as well as why God deals with believers the way He does (as a type of the second Adam in his covenant headship). On the one hand, Noah is a sinner saved by grace. But on the other hand, he is a type of Christ the second Adam in that his whole family was saved only because of and through and in union with him. So it is here with Abraham. He is a sinner saved by grace, but he's also a picture here of the second Adam, as Paul wrote in Romans 5:18-19: “So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men. For as through the one man's disobedience, the many were made sinners, even so through the obedience of the One the many will be made righteous.”
17 Bruce Waltke puts it this way in his commentary on Genesis: “Abraham’s obedience prefigures the active obedience of Christ, who secures the covenantal blessings for Abraham’s innumerable offspring.” (p311). The Spirit of the Reformation Study Bible likewise affirms this truth: “Abraham's obedience prefigured the active obedience of Christ, who secured the covenantal blessings for Abraham's innumerable offspring who share his faith in the God who gives life to the dead.” It might be argued at this point that this is irrefutable Scriptural evidence that God fulfills His promises to us by means of our faith plus our obedience. For God had promised this same thing earlier to Abraham, and now, along with this same promise, the Lord adds this qualification: “because you have obeyed My voice.” So that it seems that it was not truly by faith alone (as we've been advocating) that Abraham received and inherited the promises, but a mixture of his faith and his obedience; indeed, faith plus obedience. To this objection, we would cite another Scripture a few chapters later. For the Lord uses the very same language in telling Isaac the same truth, when He declares to him in Genesis 26:4-5: “I will multiply your descendants as the stars of heaven and will give your descendants all these lands; and by your descendants all the nations of the earth shall be blessed; because Abraham obeyed Me and kept My charge, My commandments, My statutes and My laws.” Now, this Scripture fully refutes the objection; for it uses the very same language to teach us something completely different than what is alleged to be taught in Genesis 22:18. Thus, Genesis 26:4-5 helps us to truly and rightly interpret Genesis 22:18. And what we find is this: In Genesis 22:18, we're told that the nations would be blessed because Abraham obeyed the Lord. But notice what is said in Genesis 26:4-5; here, the Lord tells Isaac that the nations would be blessed—once again—because Abraham obeyed the Lord. Now, if the intended meaning of Genesis 22:18 was that Abraham inherited the promises in and through his obedience, then we would find the Lord affirming the same truth to Isaac; but here with Isaac we find the Lord affirming a completely different truth. For in Genesis 26:4-5, the Lord does not tell Isaac, as He had told Abraham: the nations will be blessed because you, Isaac, have obeyed Me. But to the contrary, the Lord tells Isaac: the nations will be blessed because Abraham obeyed Me. Isaac is blessed, and the nations are blessed—not because of their own obedience—but because of the obedience of Another.