We continue our study by reviewing 3:10-14 and continue to verse 18 where we see Paul saying that Abraham received the promise through faith and that through Christ the blessings of Abraham has come to the Gentiles.
Verse 15: Brethren, I speak after the manner of men; Though it be but a man's covenant, yet if it be confirmed, no man disannulleth, or addeth thereto. His point here is that in response to the covenant that God made with Abraham, he can only think as a mere mortal, and that means that God made a deal with Abraham and He was not going to change his mind by getting rid of it or adding to it.
Verse 16: Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. So, back to the promises that God gave to Abraham and his descendants; they involved a land and a seed. He mentioned this when writing to the Romans when he said, Who are Israelites; to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises; Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen (Romans 9:4-5) and Now I say that Jesus Christ was a minister of the circumcision for the truth of God, to confirm the promises made unto the fathers: (Romans 15:8).
Notice that he says very clearly that the promise was made to Abraham and is seed and He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. He then further clarifies that this seed of which he speaks is none other than Christ. That means that the land of Israel is the inheritance of Christ and the Abrahamic Covenant will be ultimately fulfilled in Christ.
This is where many translations go off the rails in that while they may translate this verse correctly, they do not do so in the Old Testament passages that Paul is referring to. For example, in Genesis 13:15 and Genesis 17:8 they translate seed as offspring and descendants, yet the word for seed is always in the singular and never in the plural. To do so removes the specific reference to Christ that it clearly is.
Verses 17-18: And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect. For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise. Again, Paul is pointing out that the covenant given to Abraham by faith was in Christ just like the gospel that he preached, and the law had no bearing on it since it wasn't given until 430 years later.
His conclusion is that the promises made to Abraham were by faith and not law, therefore, the two should not be intermixed, i.e., complete in the flesh what was begun in the Spirit (cf. verse 3).