Galatians 3:29 If you belong to Christ, then you are Abraham's seed, and heirs according to the promise.
Here is Paul’s final summation before moving on to his next argument (although the next section is similar in tone and content). Here, though, the focus reverses. Throughout Chapter 3, Paul has emphasized the Jewish cultural concepts, essentially debunking their importance as far as acceptability to God is concerned, e.g., being a “child of Abraham,” viewing the law as a curse, and “Abraham’s seed.” He’s also emphasized common estate law and the social constructs of the “pedagogue” type servant. All these things serve to show us the way to Christ. His “”wrap up verse” flips the focus, but in a way to show proper emphasis – if we “belong to Christ,” then we are truly “Abraham’s seed.” It is Jesus that ties us to Abraham’s people, to Abraham’s blessing, to Abraham’s promise, no matter what our ethnic connection might be. If we “belong to Christ,” we are heirs “according to the promise.” Jesus again ties us in. Perhaps I am making too much of this in the context of sentence structure, but by starting with “If we belong to Christ,” rather than “you are Abraham’s seed if you belong to Christ,” Paul is showing us where the emphasis needs to be! On Jesus! NOT on ethnicity, culture, or what we do!
Its also interesting that Paul’s play on words back in Galatians 3:16 appears to be "out the window," in a sense. But as I discussed at length in the comments on 3:16, this is a play on words with a divine purpose. Paul uses the focus on singular, rather than plural “seed" as an argument technique, and to show the true emphasis on the concept of who the real “seed” was. But here, he shows that the reason for using an ambiguous word had a purpose in God – it is actually interpreted BOTH WAYS! Jesus was the singular seed. Through Him we all became the plural seed(s). He also adds the concept that we are “heirs.” This not only ties in with his examples of the covenant/last will and testament in verses 15-18, and the pedagogue servant in verse 24, but with the traditional Jewish concept of “Abraham’s seed.” For it was common to leave one’s estate for a single heir, and then provide that it go to others upon that heir’s death. That is what happened for us. God’s “heir,” – the one “seed” – Jesus, died on the cross, passing his inheritance under the last will – the “covenant” – on to all of us who believe in Him. In a legal sense, then, the one seed splits into many seeds – and the original, traditional way the Jews understood the contextual concept of the “seed” or “offspring” of Abraham as an infinite number, as a nation of people, becomes true as well. Paul’s little play on words with singular/plural “seed” is not just some game. Its a phrase inspired by the Holy Spirit to show that in Jesus, we are all part of God’s family. Abraham’s seed is singular AND plural, and that is so like God’s nature. The focus must be on Jesus, and OUR RELATIONSHIP with Jesus!