What does Galatians 3:16 mean?
In the previous verses, Paul declared that Christ redeemed—bought out of slavery—all those under the curse of the law by becoming that curse Himself. He paid the price of death and separation from God. What did that gain? He made it possible for even non-Jews (Gentiles) to become the children of Abraham by faith. It allowed them to receive the blessings that come with that relationship.But can God's promises to Abraham and his descendants really be claimed by non-Jewish people all these centuries later? The Judaizers would apparently say no, perhaps claiming that the law of Moses took the place of God's promises to Abraham. Now Gentiles who wanted to be included in God's family must be circumcised and follow the law, or so they said.
But Paul insists that a covenant cannot be revoked, even by new agreements later on. God declared Abraham righteous—"justified"—because of his faith. God made promises of great blessings to Abraham's offspring, on the basis of that faith. Now Paul insists the offspring God was referring to was, in fact, one man: Christ Himself. Paul is not saying that the promises to Abraham were not for the rest of his descendants, but that the focus of those promises was one singular, offspring: Jesus Christ.
Jesus, during His time on earth, was a fully human Jewish man in addition to being fully God in human form. Matthew 1 tracks the genealogy of Abraham all the way to Jesus. Christ was Abraham's descendant and would become, by God's covenant, the focus of all of God's promises to Abraham. Paul will go on to show, then, that all who are in Christ are included in those covenant promises, as well.