9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
[AD 220] Tertullian on Galatians 2:9
Now they certainly would not have been surprised at his having become a preacher instead of a persecutor, if his preaching were of something contrary; nor, moreover, would they have "glorified the Lord," because Paul had presented himself as an adversary to Him They accordingly even gave him "the right hand of fellowship," as a sign of their agreement with him, and arranged amongst themselves a distribution of office, not a diversity of gospel, so that they should severally preach not a different gospel, but (the same), to different persons, Peter to the circumcision, Paul to the Gentiles.

[AD 220] Tertullian on Galatians 2:9
Accordingly, the false brethren who were the spies of their Christian liberty must be thwarted in their efforts to bring it under the yoke of their own Judaism before that Paul discovered whether his labour had been in vain, before that those who preceded him in the apostolate gave him their right hands of fellowship, before that he entered on the office of preaching to the Gentiles, according to their arrangement with him. He therefore made some concession, as was necessary, for a time; and this was the reason why he had Timothy circumcised, and the Nazarites introduced into the temple, which incidents are described in the Acts.

[AD 220] Tertullian on Galatians 2:9
Rightly, then, did Peter and James and John give their right hand of fellowship to Paul, and agree on such a division of their work, as that Paul should go to the heathen, and themselves to the circumcision. Their agreement, also, "to remember the poor" was in complete conformity with the law of the Creator, which cherished the poor and needy, as has been shown in our observations on your Gospel.

[AD 311] Methodius of Olympus on Galatians 2:9
Since then the children have invited us, and have given unto us the right hand of fellowship,

[AD 370] Gaius Marius Victorinus on Galatians 2:9
That is, those who supported the church were like pillars supporting roofs and other things. “These men, then,” he says, “being of such quality and so great, gave me their right hands, that is, joined in friendship, peace and steadfastness and declared that they had only one gospel. In view of this accord, Galatians, you are sinning and follow neither my gospel nor that of Peter, James and John, who are the pillars of the church, when you add things that are not approved by any of them.”

[AD 370] Gaius Marius Victorinus on Galatians 2:9
“Not to me alone,” [he says], “did they give the right hand of fellowship, but also to Barnabas who was my companion.” He made the addition so that it should not appear that he alone had received the trust.

[AD 384] Ambrosiaster on Galatians 2:9
Just as he allots to Peter companions who were the outstanding men among the apostles, so he joins to himself Barnabas, who was associated with him by God’s appointment. Yet he claims that the grace of his primacy was entrusted to him alone by God, just as the primacy among the apostles was entrusted solely to Peter.

[AD 395] Gregory of Nyssa on Galatians 2:9
Since we must also ascertain how it is possible to become a “pillar,” so that we too may become worthy of this calling, we ought to hear this again from the dictum of the apostle Paul, who says that the pillar is “the foundation of truth.”

[AD 407] John Chrysostom on Galatians 2:9
Ver. 9. "And when they perceived the grace that was given unto me, James and Cephas and John, they who were reputed to be pillars, gave to me and Barnabas the right hands of fellowship."

He says not when they "heard," but when they "perceived," that is, were assured by the facts themselves, "they gave to me and Barnabas the right hands of fellowship." Observe how he gradually proves that his doctrine was ratified both by Christ and by the Apostles. For grace would neither have been implanted, nor been operative in him, had not his preaching been approved by Christ. Where it was for the purpose of comparison with himself, he mentioned Peter alone; here, when he calls them as witnesses, he names the three together, "Cephas, James, John," and with an encomium, "who were reputed to be pillars." Here again the expression "who were reputed" does not impugn the reality of the fact, but adopts the estimate of others, and implies that these great and distinguished men, whose fame was universal, bore witness that his preaching was ratified by Christ, that they were practically informed and convinced by experience concerning it. "Therefore they gave the right hands of fellowship" to me, and not to me only, but also to Barnabas, "that we should go unto the Gentiles, and they unto the Circumcision." Here indeed is exceeding prudence as well as an incontrovertible proof of their concord. For it shows that his and their doctrine was interchangeable, and that both approved the same thing, that they should so preach to the Jews, and he to the Gentiles. Wherefore he adds,

Ver. 9. "That we should go unto the Gentiles and they unto the Circumcision."

Observe that here also he means by "the Circumcision," not the rite, but the Jews; whenever he speaks of the rite, and wishes to contrast it, he adds the word "uncircumcision;" as when he says, "For circumcision indeed profits, if you be a doer of the law; but if you be a transgressor of the law, your circumcision has become uncircumcision." [Romans 2:25] And again, "Neither circumcision avails any thing, nor uncircumcision." But when it is to the Jews and not to the deed that he gives this name, and wishes to signify the nation, he opposes to it not uncircumcision in its literal sense, but the Gentiles. For the Jews are the contradistinction to the Gentiles, the Circumcision to the Uncircumcision. Thus when he says above, "For He that wrought for Peter into the Apostleship of the Circumcision, wrought for me also unto the Gentiles;" and again, "We unto the Gentiles and they unto the Circumcision," he means not the rite itself, but the Jewish nation, thus distinguishing them from the Gentiles.

[AD 420] Jerome on Galatians 2:9
Three times above we read that the apostles were “reputed.” … And so I was wondering what this word meant. Now he has delivered me from all doubt when he describes them as those “who appeared to be pillars.” Therefore it means the apostles, and above all Peter, James and John, two of whom were deemed fit to go up the Mount with Jesus. One of these introduces the Savior in the Apocalypse saying “He who has overcome I shall make him a pillar in the temple of my God.” This teaches us that all believers who have overcome the enemy can become pillars of the church.

[AD 458] Theodoret of Cyrus on Galatians 2:9
They knew this from the facts; for [he says] “just as divine grace worked with Peter for the preaching to the Jews, so it collaborated with me for the salvation of the Gentiles.”