What did the Judaizers say you must do to be saved in addition to believing?
The Judaizers claimed that faith in Paul’s Gospel was insufficient for salvation, insisting that believers must also practice circumcision and keep the Law of Moses. They taught that without these additions, a person could not be saved, thereby corrupting the truth of salvation by faith plus nothing.
Les explains that Paul’s Gospel declares salvation is by faith plus nothing. The Judaizers, however, came in saying you cannot be saved that way; you must also practice circumcision and keep the Law of Moses, or you cannot be saved. Les identifies this as a pollution or corruption of the truth, like mixing water with wine. That is why Paul wrote the whole letter to the Galatians—to correct them from this error of believing something corrupt and perverted.