v26-27: “in Christ Jesus you are all sons of God” – Christianity is not about living in a certain way in the hope that one day, if we’ve done a good enough job, we’ll be welcomed into heaven. It’s about being in Christ, united with him, which means we are God’s sons and daughters now.
Paul points to baptism to remind the Galatians that they were in Christ from the moment they became Christians. We tend to wait a while before baptising people, and think of it as mainly a witness to other people of our profession of faith, but Paul wants the Galatians to look back to their baptism as a sign to themselves that they have been united with Christ from the moment they repented and believed the gospel. Although we hopefully experience getting closer in our relationship with God as we continue in the Christian life, we’re adopted into his family right from the start.
Paul also uses this phrase “you… have put on Christ”, reminding the Galatians that their adoption into the family of the holy God is justified not because they’ve cleaned their sin off themselves and worked up their own righteousness, but because they’ve put on Christ’s righteousness.
The false teachers were telling the Galatians, “yes your faith in Jesus is good, but you need to do this as well…” but knowing that our adoption into God’s family is based on us being clothed in Christ’s righteousness, it’s ridiculous to think we could in any way improve on it or make ourselves more secure than we already are in Christ.
v28: “neither… nor…” – Having talked about our unity with God as we’re “in Christ” and “sons of God”, there are implications for our relationships with other Christians. Since they’re just as united with Christ as we are, barriers that would otherwise divide us based on culture, class or gender are removed. Not that our differences cease to exist. Men and women still have different roles to play, and people who come from different cultural backgrounds don’t need to all start conforming to the same ways of doing things, but our unity with Christ should transcend our differences. One group is not superior to another. “You are all one in Christ Jesus”.
v29: “if you are Christ’s, you are Abraham’s offspring, heirs according to promise” – Presumably the people telling the Galatians they should be circumcised were selling it on the basis of the blessings you get by being a descendant of Abraham. Paul clarifies that if you are Christ’s, you are already a descendant of Abraham. You’re an heir according to promise. There’s no additional blessing to be had by conforming to Abrahamic tradition.
It’s encouraging that we’re heirs according to promise, not according to our performance, but I guess we also need to watch out that we don’t try to make people conform to our cultural traditions.