But with regard to the countenance of Peter and the rest of the apostles, he tells us that "fourteen years after he went up to Jerusalem," in order to confer with them about the rule which he followed in his gospel, lest perchance he should all those years have been running, and be running still, in vain, (which would be the case, ) of course, if his preaching of the gospel fell short of their method.
These men he had as witnesses, through whom he proved that his gospel was given to him through revelation, seeing that he said “Barnabas went up with me,” and he also took Titus, whose faith and gospel were approved by everyone.
His renown had been growing for a long time among all the Jews, though he had not been seen face to face … but on account of the law he had acquired a bad reputation among the Jews, as though his preaching was out of harmony with the preaching of the other apostles. Many were having doubts on account of this, which were sufficient to make the Gentiles anxious, in case they had been trained in something other than that which was preached by the apostles who had been with the Lord. For on this precise occasion the Galatians were undermined by Jews who were saying that Paul taught something other than Peter taught. This is the reason for his going up to Jerusalem, at the bidding of the Lord’s revelation, disclosing to them the implications of his preaching, with Barnabas and Titus as witnesses of his preaching, one from the Jews and one from the Gentiles, so that if any took offense at him it might be assuaged by their testimony.
His first journey was owing to his desire to visit Peter, his second, he says, arose from a revelation of the Spirit.
"And I laid before them the Gospel which I preach among the Gentiles, but privately before them who were of repute, lest by any means I should be running or had run in vain."
What is this, O Paul! thou who neither at the beginning nor after three years wouldest confer with the Apostles, dost thou now confer with them, after fourteen years are past, lest thou shouldest be running in vain? Better would it have been to have done so at first, than after so many years; and why didst thou run at all, if not satisfied that thou wert not running in vain? Who would be so senseless as to preach for so many years, without being sure that his preaching was true? And what enhances the difficulty is, that he says he went up by revelation; this difficulty, however, will afford a solution of the former one. Had he gone up of his own accord, it would have been most unreasonable, nor is it possible that this blessed soul should have fallen into such folly; for it is himself who says, "I therefore so run, as not uncertainly; so fight I, as not beating the air." (1 Cor. ix: 26.) If therefore he runs, "not uncertainly," how can he say, "lest I should be running, or had run, in vain?" It is evident from this, that if he had gone up without a revelation, he would have committed an act of folly. But the actual case involved no such absurdity; who shall dare to still harbor this suspicion, when it was the grace of the Spirit which drew him? On this account he added the words "by revelation," lest, before the question was solved, he should be condemned of folly; well knowing that it was no human occurrence, but a deep Divine Providence concerning the present and future. What then is the reason of this journey of his? As when he went up before from Antioch to Jerusalem, it was not for his own sake, (for he saw clearly that his duty was simply to obey the doctrines of Christ,) but from a desire to reconcile the contentious; so now his object was the complete satisfaction of his accusers, not any wish of his own to learn that he had not run in vain. They conceived that Peter and John, of whom they thought more highly than of Paul, differed from him in that he omitted circumcision in his preaching, while the former allowed it, and they believed that in this he acted unlawfully, and was running in vain. I went up, says he, and communicated unto them my Gospel, not that I might learn aught myself, (as appears more clearly further on,) but that I might convince these suspicious persons that I do not run in vain. The Spirit foreseeing this contention had provided that he should go up and make this communication.
Wherefore he says that he went up by revelation, and, taking Barnabas and Titus as witnesses of his preaching, communicated to them the Gospel which he preached to the Gentiles, that is, with the omission of circumcision. "But privately before them who were of repute." What means "privately?" Rather, he who wishes to reform doctrines held in common, proposes them, not privately, but before all in common; but Paul did this privately, for his object was, not to learn or reform any thing, but to cut off the grounds of those who would fain deceive. All at Jerusalem were offended, if the law was transgressed, or the use of circumcision forbidden; as James says, "Thou seest, brother, how many thousands there are among the Jews of them which have believed; and they are informed of thee, that thou teachest to forsake the law." (Acts xxi: 20, et seq.) Since then they were offended he did not condescend to come forward publicly and declare what his preaching was, but he conferred privately with those who were of reputation before Barnabas and Titus, that they might credibly testify to his accusers, that the Apostles found no discrepancy in his preaching, but confirmed it. The expression, "those that were of repute," does not impugn the reality of their greatness; for he says of himself, "And I also seem to have the Spirit of God," thereby not denying the fact, but stating it modestly. And here the phrase implies his own assent to the common opinion.
(Chapter 2 - Verses 1, 2) Then after fourteen years, I went up again to Jerusalem with Barnabas, taking Titus along also. I went up by revelation, and I discussed with them the gospel that I preach to the Gentiles, but privately with those who seemed to be influential, so that I might not be running in vain or have run in vain. This matter arose because of false brothers secretly brought in, who slipped in to spy out our freedom that we have in Christ Jesus, so that they might bring us into slavery. And to speak more truthfully, the Greek word ἀνεθέμην conveys something different than what is understood among us, namely that we compare what we know with a friend and place it in their lap and conscience, so that, with equal counsel, what we know may either be approved or disapproved. Therefore, after fourteen years, he went up to Jerusalem. And he who had previously gone only to see Peter and stayed with him for fifteen days, now says that he went there to confer with the apostles about the Gospel. And he took along Barnabas, who was circumcised, and Titus, who was uncircumcised among the Gentiles, so that every word may be established by the testimony of two or three witnesses (Deut. 19:15). But it is one thing to compare, another to learn. Among those who compare, there is equality; between the teacher and the learner, the one who learns is lesser. At the beginning of faith, he saw the apostles during their journey. After seventeen years (as he himself says), he speaks fully with them and humbles himself: and lest he might be running or might have run in vain, he inquires. For a twofold reason, so that the humility of Paul, who, as a teacher, had already surpassed the apostles who came before him in the whole world of the Gentiles, might be shown: and so that the Galatians may not say that they rejected his Gospel, also condemning those who presided over the Churches in Judea. Moreover, it also teaches that for the sake of the faith of Christ and the liberty of the Gospel, he dared to lead Titus, an uncircumcised man, to those same individuals who knew more about him, who accused him of breaking the Law, destroying Moses, and completely doing away with circumcision. And in the midst of such a great multitude of Jews and his enemies, who desired to shed his blood out of zeal for the Law, neither he nor Titus gave way to fear, but stood firm in necessity. They were able to obtain forgiveness, either in terms of position or authority of the elders, or in terms of the number of churches that believed in Christ from the Jews, or in terms of time, so as not to endure such great envy at the same time. Some say that after fourteen years he went up to Jerusalem, when a dispute arose among the believers in Antioch regarding the observance or omission of the Law, as recorded in the Acts of the Apostles. It was decided to go to Jerusalem and wait for the judgment of the elders, when Paul and Barnabas themselves were sent. And this is what is written in the Latin codices: We yielded to subjection for a time, so that the truth of the Gospel would persist among you. That is why, clearly, Paul and Barnabas were sent to Jerusalem as if it were doubtful, in order to confirm by the judgment of the elders that the grace of the Gospel had also been given to the believers, and that there would be no further doubt about the omission of circumcision. For it had been commanded by the letters of the apostles that the yoke of the Law should be removed from those who believed in Christ from the Gentiles. However, it can be understood that when he says, 'I conferred with them the Gospel that I preach to the Gentiles,' he means separately to those who seemed important, so that I might not run or have run in vain, and thus it can be understood that he shared with the apostles in secret the grace of Gospel freedom and the abolishment of the old Law, because of the multitude of believing Jews who were not yet able to hear about the fulfillment and end of the Law, and who, in the absence of Paul, had falsely boasted in Jerusalem that he was going on a pointless or fruitless journey, thinking that the old Law should not be followed. Not because Paul feared that he had preached a false Gospel among the Gentiles for seventeen years; but to show his predecessors that he was not running or had run in vain, as they had thought in their ignorance.
Both [Barnabas and Titus] spent an extended time in Antioch, making a large body of converts and binding them to live according to the law of grace. But some supporters of the law who arrived from Judea tried to persuade the Gentiles to adopt the way of life according to the law But those great heralds of the truth, Paul and Barnabas, repudiated the teaching they promoted. They wished to persuade the congregation of the faithful that this was also the view of the great apostles. So they immediately went straightway to Judea, to apprise the apostles of what was going on.
[AD 202] Irenaeus on Galatians 2:1