John Chrysostom

"I thank God that I baptized none of you but Crispus and Gaius." "Why are you elate at having baptized, when I for my part even give thanks that I have not done so!" Thus saying, by a kind of divine art he does away with their swelling pride upon this point; not with the efficacy of the baptism, (God forbid,) but with the folly of those who were puffed up at having been baptizers: first, by showing that the Gift is not theirs; and, secondly, by thanking God therefore. …

Homily on 1 Corinthians 3 ↗

Theophylact of Ohrid

Why, he says, do you boast that you baptize, when I thank God that I did not baptize? He says this not in order to diminish the importance of baptism, but in order to restrain the Corinthians, who boasted of baptism. For baptism is an important matter, but to baptize is not an important one.

Commentary on 1 Corinthians ↗

Thomas Aquinas

Then when he says, I am thankful, he dismisses a false surmise. For since he had said, Was Paul then crucified for you, someone might suppose that though he had not baptized in his own name, he did baptize many people as a minister. In regard to this he does three things: first, he gives thanks for having baptized only a few; secondly, after naming the few, he adds certain others (v. 16); thirdly, he gives the reason why he did not baptize many (v. 17). He says, therefore: I give God thanks that I baptized none of you but Crispus. …

Commentary on 1 Corinthians ↗