(Verse 11 onwards) But when Peter came to Antioch, I opposed him to his face, because he stood condemned. For before certain men came from James, he was eating with the Gentiles. But when they came, he withdrew and separated himself, fearing those of the circumcision. And the rest of the Jews acted hypocritically along with him, so that even Barnabas was led astray by their hypocrisy. When I saw that they were not walking straight, according to the truth of the gospel, I said to Peter in the presence of all, 'If you, who are a Jew, live like the Gentiles and not like the Jews, how can you compel the Gentiles to live like Jews?' We are Jews by nature, and not Gentile sinners, but we know that a person is not justified by the works of the law, but through faith in Jesus Christ. Therefore, when the apostle Paul saw that the grace of Christ was in danger, he employed a new battle tactic of the old warrior, to correct the dispensation of Peter, by which he desired the salvation of the Jews, with a new dispensation of contradiction, and to resist him to his face. Not arguing against his intention, but rather publicly contradicting him, so that by Paul's argument and resistance, those who had believed from the Gentiles would be saved. Now if anyone thinks that Paul truly resisted the apostle Peter and boldly did wrong to his predecessor for the sake of the truth of the Gospel, that person's argument will not stand. For even Paul became a Jew to the Jews in order to gain the Jews, and he will be held guilty of the same hypocrisy when he shaved his head in Cenchreae and offered a sacrifice in Jerusalem (Acts 18), and when he circumcised Timothy (Ibid., 16), and practiced foot-washing, which are clearly ceremonial practices of the Jews. Therefore, if the one who was sent to preach to the Gentiles did not think it necessary to say: 'Be without offense to the Jews and to the Church of God' (1 Corinthians 10:32); how can I please everyone in all things, not seeking my own profit, but the profit of many, so that they may be saved? And he did certain things that were contrary to the freedom of the Gospel, so as not to scandalize the Jews. With what authority, with what audacity does he dare to reprehend this in Peter, who was an apostle of the circumcision, when he himself, the apostle of the Gentiles, is accused of committing the same? But as we have already said, he yielded to the public opinion, to Peter and the rest, so that the hypocrisy of observing the Law, which was harming those who had believed from the Gentiles, would be corrected by the hypocrisy of correction, and both peoples would be saved, both those who praise circumcision follow Peter; and those who do not want to be circumcised, preach Paul's freedom. But what he said was blameworthy, therefore he moderated the fasting; so that we understand that he was not so blameworthy to Paul, as he separated himself from those brothers with whom he had eaten before. But a useful simulation, and one to be adopted in time, let us teach an example of King Jehu of Israel, who could not kill the priests of Baal unless he pretended to want to worship the idol, saying: 'Gather (or 'gather together') for me all the priests of Baal: for if Ahab served Baal in few things, I will serve him in many.' (4 Kings 10:18). And David, when he changed his appearance before Abimelech, and who dismissed him and went away. (1 Kings 21) And it is not surprising, even though righteous men, nevertheless, pretend for a time, for their own and others’ salvation, when our Lord Himself, not having sin nor the flesh of sin, assumed the pretense of sinful flesh, so that, condemning sin in the flesh, He would make us the righteousness of God in Himself. Certainly, Paul had read in the Gospel the Lord commanding: But if your brother sins against you, go and correct him between you and him alone. If your brother sins against you, rebuke him; and if he repents, forgive him. (Luke 17:3) And in what way, when he even commanded this to be done to the least of the brothers, did he dare to rebuke the greatest of the apostles so boldly and steadfastly in public; unless it had pleased Peter to be rebuked in this way, and Paul had not done him any harm, about whom he had said before: I went to Jerusalem to see Peter, and I stayed with him for fifteen days: but I saw none of the other apostles. And again: For he who worked in Peter for the apostleship of the circumcision. And below: Peter and James and John, who seemed to be pillars, and the others whom he praises in his praises. Many times, when I was a young man in Rome, I would engage in debates on fictitious lawsuits and exercise myself in true competitions. I would run to the courts of the judges, and I would see the most eloquent orators contending with each other with such bitterness that they would often neglect their duties and turn to personal insults, biting each other with jokes. If they do this, so that they may not incur any suspicion of prevarication, and deceive the surrounding people, what do we think the great pillars of the Church, Peter and Paul, and the vessels of wisdom, ought to have done among the dissenting Jews and Gentiles? Unless it was for the purpose of making their pretended contention the peace of the believers, and the faith of the Church might be established by a holy dispute among them. There are some who think that Cephas, whom Paul writes that he confronted to his face, is not the apostle Peter, but another one of the seventy disciples called by that name. They say that Peter could not have avoided the company of the Gentiles, as he had also baptized the centurion Cornelius. And when he went up to Jerusalem, those who were of the circumcision argued against him, saying: Why did you go to men uncircumcised and eat with them? After recounting the vision, he concluded his response with these words: Therefore, if God gave them the same gift as he gave us when we believed in the Lord Jesus Christ, who was I to hinder God? When they heard this, they fell silent and glorified God, saying, 'So then, even to the Gentiles God has granted repentance unto life.' Especially since the writer of the history, Luke, makes no mention of this disagreement; nor does he ever say that Peter was in Antioch with Paul, and that Porphyry was blaspheming; but if it is believed that Peter erred or that Paul insolently refuted the chief of the apostles, first it must be answered that we do not know the name of some other Cephas, unless it is the one who is called both Cephas and Peter in the Gospel, in Paul's other Epistles, and also in this very passage. Not that Peter signifies one thing and Cephas another, but that as we call the rock in Latin and Greek, so the Hebrews and Syrians, because of the similarity of their languages, name it Cephas. Moreover, the entire argument of the epistle, which is indirectly mentioned concerning Peter, James, and John, contradicts this interpretation. It is not surprising that Luke has remained silent on this matter, considering that he has omitted many other things that Paul claims to have endured, by the liberty of a historian, and it is not necessarily contradictory if one deemed worthy of recounting what another left out among other things for a different reason. Lastly, we have learned that Peter was the first bishop of the Church of Antioch, and then transferred to Rome, which Luke completely omitted. Finally, if we are to create another person called Cephas because of Porphyry's blasphemy, so that Peter is not thought to have erred, countless divine Scriptures will have to be erased, which he condemns because he does not understand. But also against Porphyry, we will fight in another way if Christ commands it: now let us continue with the rest.
Well, but Marcion, finding the Epistle of Paul to the Galatians (wherein he rebukes even apostles ) for "not walking uprightly according to the truth of the gospel," as well as accuses certain false apostles of perverting the gospel of Christ), labours very hard to destroy the character of those Gospels which are published as genuine and under the name of apostles, in order, forsooth, to secure for his own Gospel the credit which he takes away from them.
What then should we understand by “their insincerity”? Even Peter and Barnabas and the other Jews had not truly gone to the length of living their lives according to Jewish practice. They even pretended to do so as an ad hoc measure, because of the fears of those around them. And therefore, he says, even Barnabas acquiesced in their insincerity.
Ver. 13. "Insomuch that even Barnabas was carried away with their dissimulation."
Be not surprised at his giving this proceeding the name of dissimulation, for he is unwilling, as I said before, to disclose the true state of the case, in order to the correction of his disciples. On account of their vehement attachment to the Law, he calls the present proceeding "dissimulation," and severely rebukes it, in order effectually to eradicate their prejudice. And Peter too, hearing this joins in the feint, as if he had erred, that they might be corrected by means of the rebuke administered to him. Had Paul reproved these Jews, they would have spurned at it with indignation, for they held him in slight esteem; but now, when they saw their Teacher silent under rebuke, they were unable to despise or resist Paul's sentence.
Paul never fell into any pretense, for he everywhere observed a principle which seemed fitting both to Gentile and to Jewish churches, that he should nowhere take away a custom whose observation did not prevent the receiving of God’s kingdom.… Peter, however, when he came to Antioch, was rebuked by Paul not because he observed the Jewish custom in which he was born and reared, although he did not observe it among the Gentiles, but because he wanted to impose it on the Gentiles. This happened after seeing certain persons come from James—that is, from Judea, since James was the head of the church in Jerusalem. It was therefore in fear of those who still thought that salvation resided in these observances that Peter separated himself from the Gentiles and pretended to consent in imposing those burdens of servitude on the Gentiles.
[AD 420] Jerome on Galatians 2:11-13