John Chrysostom

But seeing that whoso is blamed is unabashed so long as he hath no witnesses, observe how, not permitting them to deny the fact, he adduces some to bear witness. "For it hath been signified unto me concerning you, my brethren, by them which are of the household of Chloe." Neither did he say this at the very beginning, but first he brought forward his charge; as one who put confidence in his informants. Because, had it not been so, he would not have found fault: for Paul was not a person to believe lightly. …

Homily on 1 Corinthians 3 ↗

Theophylact of Ohrid

"For it has been made known to me concerning you, my brethren, by those of the household of Chloe." Lest they begin to deny it, he brings forward witnesses, and lest it seem as though he is inventing them, he names them, saying: "from the household of Chloe" (there was a house in Corinth called Chloe's). He also calls them "brethren": for although their sin was evident, nothing prevented him from calling them brethren. …

Commentary on 1 Corinthians ↗

Thomas Aquinas

Then when he says, It has been reported, he shows why it was necessary to warn them, namely, because they were burdened with the vice of contention. As if to say: It is necessary to induce you to this, because it has been reported to me, my brethren, by Chloe's people, i.e., from a certain villa subject to the jurisdiction of the Corinthians. …

Commentary on 1 Corinthians ↗