Paul says that he stood up before the entire group and publicly denounced Peter, as well as his own co-worker Barnabas: “If you though a Jew, live like a Gentile and not like a Jew, how can you compel the Gentiles to live like Jews?” (Galatians 2:14). The charge as stated here by Paul really makes no sense, since even if Peter and Barnabas had eaten unfit food at the table of the Gentiles, they would not thereby be compelling the Gentiles to live like Jews. But the idea that Peter would have disregarded dietary laws in the first place goes against everything we know of his leadership status alongside James in an observant Jewish-Christian community following the Torah. It is possible Peter was simply sitting with the Gentiles, not actually eating with them, but that when those from James arrived, Peter joined them at their kosher table and Paul interpreted this as a kind of social shunning.
But it is likely something much more significant is going on here, something Paul would never want to let out. If Paul’s charge that Peter was “compelling the Gentiles to live like Jews” has any force at all, it must reflect Peter’s sympathy with the idea that it was a perfectly fine and good thing if Gentiles who had become followers of Jesus were subsequently drawn toward Judaism and decided to convert. The issue would not be compulsion but free choice. Since the main issue Paul is addressing in the letter of Galatians is that his Gentile converts should not, under any circumstances, convert to Judaism, but remain as they are, Paul’s denunciation of Peter and Barnabas likely reflects his consternation at their welcoming Gentiles who wanted to convert. Judaism did welcome sincere converts and there is every reason to think that Peter, James, and the others would have done the same. Requiring conversion and welcoming those who might choose it, however, are two entirely separate issues. Paul’s position with his Gentile converts was that they did not need to convert to Judaism or keep the Torah in order to have a right relationship with God. That is not the same as saying that those who might choose to convert, having joined the Christian community as Gentiles, should be forbidden to do so. And that is the position that Paul took with his own converts. He tells them that if they receive circumcision, they are “cut off from Christ” (Galatians 5:2–4).
That Barnabas sides with Peter is quite telling, since he had spent years loyally working with Paul as a missionary partner. According to Acts he was a Levite, a member of a group that required the strictest observance of Torah, and he had the trust of the Jerusalem apostles (Acts 4:36). Apparently at this confrontation Paul begins to reveal a side of his teachings about the Torah of which even Barnabas, who had worked by his side, was not aware; otherwise surely Barnabas would have supported Paul on this occasion. It is also noteworthy that Barnabas is the one, according to Acts, who first introduced Paul to the Jerusalem church and vouched for him at Antioch as well (Acts 9:27; 11:25–26). Barnabas was closely tied to James and the Jerusalem apostles. He had been sent by them to provide leadership to the newly formed group in Antioch some decades earlier (Acts 11:22). The relations between Antioch and Jerusalem were close, as evidenced by the delegation from James arriving shortly before Paul’s outburst (Galatians 2:12).
As noted, we have only Paul’s side of the story and one should not assume that Peter and Barnabas agreed with Paul or were somehow properly rebuked and put in their place by Paul’s harsh denunciation. They might well have defended themselves quite ably against his charges and it is very possible that given the circumstances it was Paul who was rebuked at Antioch. If Peter had apologized or acknowledged that Paul was correct, we surely would have Paul including that fact as part of his account. The fierceness of this confrontation was likely the first crack in the façade of harmony between Paul and the Jerusalem leadership.
It is quite significant that Acts records that right after the Jerusalem meeting of A.D. 50, when Paul and Barnabas had returned to Antioch, they had a “sharp contention” and permanently split, never to work together again (Acts 15:39). Acts says the reason was whether to take Mark with them as they planned their next missionary trip—Paul objected and Barnabas wanted him along. It seems more likely that the confrontation with Peter and Barnabas over eating with the Gentiles, which Paul reports and Acts ignores, may have been the real cause of their bitter split.