The Apostles, as I said before, permitted circumcision at Jerusalem, an abrupt severance from the law not being practicable; but when they come to Antioch, they no longer continued this observance, but lived indiscriminately with the believing Gentiles which thing Peter also was at that time doing. But when some came from Jerusalem who had heard the doctrine he delivered there, he no longer did so fearing to perplex them, but he changed his course, with two objects secretly in view, both to avoid offending those Jews, and to give Paul a reasonable pretext for rebuking him. For had he, having allowed circumcision when preaching at Jerusalem, changed his course at Antioch, his conduct would have appeared to those Jews to proceed from fear of Paul, and his disciples would have condemned his excess of pliancy. And this would have created no small offense; but in Paul, who was well acquainted with all the facts, his withdrawal would have raised no such suspicion, as knowing the intention with which he acted. Wherefore Paul rebukes, and Peter submits, that when the master is blamed, yet keeps silence, the disciples may more readily come over. Without this occurrence Paul's exhortation would have had little effect, but the occasion hereby afforded of delivering a severe reproof, impressed Peter's disciples with a more lively fear. Had Peter disputed Paul's sentence, he might justly have been blamed as upsetting the plan, but now that the one reproves and the other keeps silence, the Jewish party are filled with serious alarm; and this is why he used Peter so severely. Observe too Paul's careful choice of expressions, whereby he points out to the discerning, that he uses them in pursuance of the plan, (οἰκονομίας) and not from anger.
His words are, “When Cephas came to Antioch, I resisted him to the face, because he stood condemned;” that is, not by me but by others; had he himself condemned him, he would not have shrunk from saying so. And the words, “I resisted him to the face,” imply a scheme for had their discussion been real, they would not have rebuked each other in the presence of the disciples, for it would have been a great stumblingblock to them. But now this apparent contest was much to their advantage; as Paul had yielded to the Apostles at Jerusalem, so in turn they yield to him at Antioch. The cause of censure is this, “For before that certain came from James,” who was the teacher at Jerusalem, “he did eat with the Gentiles, but when they came he drew back and separated himself, fearing them that were of the Circumcision:” his cause of fear was not his own danger, (for if he feared not in the beginning, much less would he do so then,) but their defection. As Paul himself says to the Galatians, “I am afraid of you, lest by any means I have bestowed labor upon you in vain:” and again, “I fear lest by any means as the serpent beguiled Eve,...so your minds should be corrupted.” Thus the fear of death they knew not, but the fear lest their disciples should perish, agitated their inmost soul.
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.
Ver. 14. “But when I saw that they walked not uprightly according to the truth of the Gospel.”
Neither let this phrase disturb you, for in using it he does not condemn Peter, but so expresses himself for the benefit of those who were to be reformed by the reproof of Peter.
Ver. 14. “I said unto Cephas before them all.”
Observe his mode of correcting the others; he speaks “before them all,” that the hearers might be alarmed thereby. And this is what he says—
Ver. 14. “If you, being a Jew, livest as do the Gentiles, and not as do the Jews, how do you compel the Gentiles to live as do the Jews?”
But it was the Jews and not the Gentiles who were carried away together with Peter; why then does Paul impute what was not done, instead of directing his remarks, not against the Gentiles, but against the dissembling Jews? And why does he accuse Peter alone, when the rest also dissembled together with him? Let us consider the terms of his charge; “If you, being a Jew, livest as do the Gentiles, and not as do the Jews, how do you compel the Gentiles to live as do the Jews?” for in fact Peter alone had withdrawn himself. His object then is to remove suspicion from his rebuke; had he blamed Peter for observing the Law, the Jews would have censured him for his boldness towards their Teacher. But now arraigning him in behalf of his own peculiar disciples, I mean the Gentiles, he facilitates thereby the reception of what he has to say which he also does by abstaining from reproof of the others, and addressing it all to the Apostle. “If you,” he says, “being a Jew, livest as do the Gentiles, and not as do the Jews;” which almost amounts to an explicit exhortation to imitate their Teacher, who, himself a Jew, lived after the manner of the Gentiles. This however he says not, for they could not have received such advice, but under color of reproving him in behalf of the Gentiles, he discloses Peter's real sentiments. On the other hand, if he had said, Wherefore do you compel these Jews to Judaize? His language would have been too severe. But now he effects their correction by appearing to espouse the part, not of the Jewish, but of the Gentile, disciples; for rebukes, which are moderately severe, secure the readiest reception. And none of the Gentiles could object to Paul that he took up the defense of the Jews. The whole difficulty was removed by Peter's submitting in silence to the imputation of dissimulation, in order that he might deliver the Jews from its reality. At first Paul directs his argument to the character which Peter wore, “If you, being a Jew:” but he generalizes as he goes on, and includes himself in the phrase,
Ver. 15. “We being Jews by nature, and not sinners of the Gentiles.”
These words are hortatory, but are couched in the form of a reproof, on account of those Jews. So elsewhere, under cover of one meaning he conveys another; as where he says in his Epistle to the Romans, “But now I go unto Jerusalem, ministering unto the saints.” Here his object was not simply to inform them of the motive of his journey to Jerusalem, but to excite them to emulation in the giving of alms. Had he merely wished to explain his motive, it would have sufficed to say, “I go to ministering unto the saints;” but now observe what he says in addition; “For it has been the good pleasure of Macedonia and Achaia to make a certain contribution for the poor among the saints that are at Jerusalem. Yea, it has been their good pleasure and their debtors they are.” And again, “For if the Gentiles have been made partakers of their spiritual things, they owe it to them, also to minister unto them in carnal things.”
Observe how he represses the high thoughts of the Jews; preparing for one thing by means of another, and his language is authoritative. “We being Jews by nature, and not sinners of the Gentiles.” The phrase, “Jews by nature,” implies that we, who are not proselytes, but educated from early youth in the Law, have relinquished our habitual mode of life, and be taken ourselves to the faith which is in Christ.
Ver. 16. “Knowing that a man is not justified by the works of the Law, save through faith, in Jesus Christ, even we believed on Christ Jesus.”
Source: Commentary on Galatians (New Advent)