In preparing to preach on Genesis 22, where Abraham was commanded by God to sacrifice his son Isaac on Mount Moriah, I consulted numerous commentaries on Genesis. But I also had a glance at John Calvin's commentary on Hebrews 11:17-19. Commenting on Hebrews 11:19, Calvin mentions the opinions of other interpreters of the text,
However, I do not dislike what some say, who think that our flesh, which is subject to death, is set forth in the ram which was substituted for Isaac. I also allow that to be true which some have taught, that this sacrifice was a representation of Christ.
But, he goes on to say that his concern as a commentator is not to say what might be said about the text, but to explain what the text itself says,
I have now to state what the Apostle meant, not what may in truth be said; and the real meaning here, as I think, is, that Abraham did not receive his Son otherwise than if he had been restored from death to new life.
Should we not also make a similar distinction in our preaching between the strict grammatico-historical meaning of a text and the broad redemptive-historical significance of the passage under consideration? Not that we focus on the one at the expense of the other, but that we be careful not to dump the whole weight of developed biblical revelation on a earlier text of Scripture. Doing so would be to ignore the progressive character of Holy Scripture.
Take Genesis 22 as a case in point. The burden of the passage is not primarily about Jesus' substitutionary atoning death. Rather, it concerns the Lord testing Abraham's faith, Genesis 22:1, the Lord's provision of a ram in place of Isaac Genesis 22:12-14, and the Lord's renewal of the covenant promises, Genesis 22:15-18. In essence, that is what the text says.
But there is more that might be properly said about the text than that. Isaac was Abraham's "seed" in whom the nations would be blessed, (Genesis 21:12, 17:19). The "seed" promise was originally intimated in Genesis 3:15. The "seed" of the woman would defeat the "seed" of the serpent. That saving "seed" will come from Abraham's line, Genesis 22:18. The promise is further narrowed down to one of king David's descendents, 2 Samuel 7:12-13. Jesus is identified with the line of Abraham and David in Matthew 1:1-17. Paul describes Jesus as the "seed of Abraham" in Galatians 3:16 and the "seed of David" in Romans 1:2-4 and 2 Timothy 2:8.
Abraham was called to sacrifice his "seed", although he believed that God would raise him from the dead, Genesis 22:5 cf. Hebrews 11:17-19. However, the Lord provided a ram in place of Isaac, his only son. In the case of Christ, God did not spare him, but delivered him up for us all and then raised him from the dead (Romans 8:32-34). Paul's language in Romans 8:32 (cf. Genesis 22:16), plus the reference to God's provision makes it clear that the apostle is alluding to Abraham and Isaac. See also the way in which Peter weaves together an intertexual web around the death and resurrection of Christ and his identity as the "seed of Abraham", Acts 3:13-15, 25-26. (Note a similar pattern of thought in Acts 13:16-30).
Genesis 22 in its pure grammatico-historical meaning does not say that Jesus Christ is the "seed" who died and rose again to remove God's curse from a fallen world and bring blessing to the nations (Galatians 3:13-14). But the text should not be read in isolation. Earlier revelation needs to be taken into account (i.e. Genesis 3:15) and the contribution of Genesis 22 to redemptive-historical themes unfolded progressively in Scripture needs to be traced out (i.e. Galatians 3:16, 29). We must neither deposit on Genesis 22 the full weight of the New Testament's revelation of Jesus, neither should we be blind to the witness of that text to Christ.
As Augustine pointed out with regard to the relationship between the Testaments, "The New is in the Old concealed and the Old is in the New revealed." After all, as Jesus said, Abraham saw his day and rejoiced, John 8:56. We must preach what the the Old Testament says, explaining the grammatico-historical of texts and declare what might be properly said concerning the text's testimony to Jesus. In other words we must follow the the exegetical model laid down for us by Christ and the apostles, Luke 24:44, Acts 17:2-3.