Paul is astonished to learn that the churches of Galatia have embraced a different teaching from that which they were given by Paul.1 He essentially accuses them of being religious turncoats.2 Later, he will affirm that this different teaching places an emphasis on circumcision (Galatians 5:2–6; Galatians 6:12–13),3 likely being the same as that advocated by the individuals who visited Antioch (Acts 15:1). Given our sinful natures and tendencies to turn from the Lord (Exodus 32:7–8), one would not ordinarily expect Paul to be surprised that the Galatians have struggled to hold fast to the gospel. As such, it is likely that he spoke at length with them about the issue of circumcision and the Mosaic laws during his initial visit (Acts 13:38–39).
6 I am astonished that you are so quickly deserting him who called you in the grace of Christ and are turning to a different gospel