John Chrysostom

"For first of all, when ye come together in the Church, I hear that divisions exist among you." And he saith not, "For fear that you do not sup together in common;" "for I hear that you feast in private, and not with the poor:" but what was most calculated thoroughly to shake their minds, that he set down, the name of division, which was the cause of this mischief also: and so he reminded them again of that which was said in the beginning of the Epistle, and was "signified by them of the house of Chloe." "And I partly believe it." …

Homily on 1 Corinthians 27 ↗

Theophylact of Ohrid

Not immediately does he begin speaking about the meals, but first reproaches them for the fact that there are divisions among them. For indeed, it was precisely because there were divisions among them that each one ate separately. So that they would not say that those who slander us are lying, he said neither "I believe," lest he make them more shameless, nor "I do not believe," lest he appear a groundless accuser, but: I partly believe. And indeed it is likely that not all violated this custom, but a "part," that is, some.

Commentary on 1 Corinthians ↗

Thomas Aquinas

Then when he says, For in the first place, he mentions in detail how they assemble for the worse. First, he presents a judgment of guilt, saying: For in the first place, among others, namely, that you come together for the worse, when you assemble as a church, I hear that there are divisions among you, namely, through contentions, which they practiced. …

Commentary on 1 Corinthians ↗