Expositor's Bible Commentary Commentary Galatians 2:12

"For before that certain came from James, he ate with the Gentiles; but when they came, he drew back and separated himself, fearing them that were of the circumcision." — Galatians 2:12 (ASV)

Here is the reason why Peter stood condemned. He was not simply making an honest mistake. The Peter who had received a vision prior to going to the house of Cornelius (Acts 10) and who had defended Paul at the council (Acts 15:7–11) was not fooled by the arguments of the legalizers. Instead, he had gradually given in to the pressure exerted by the legalizers. In other words, Peter played the hypocrite.