Read Galatians 2:12 Using Other Translations
For before that certain came from James, he did eat with the Gentiles: but when they were come, he withdrew and separated himself, fearing them which were of the circumcision.
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.
When he first arrived, he ate with the Gentile believers, who were not circumcised. But afterward, when some friends of James came, Peter wouldn’t eat with the Gentiles anymore. He was afraid of criticism from these people who insisted on the necessity of circumcision.