Elsewhere in the New Testament, those of the circumcision group can refer to Jews (Romans 4:12), Jewish Christians (Acts 10:45; Acts 11:2; Colossians 4:11) or false teachers (Titus 1:10).1 In the context of Galatians, it is most likely a reference to Jewish Christians who thought that circumcision was necessary also for Gentile Christians. They would no doubt have held to the common Jewish understanding that it was wicked/idolatrous to eat with Gentiles at the same table (consuming the same food).2
12 For before certain men came from James, he was eating with the Gentiles; but when they came he drew back and separated himself, fearing the circumcision party.