John Chrysostom

"For if at the mouth of two witnesses or three every word shall be established, and I have come twice and spoken, and speak now also by this Epistle; it follows, I must after this keep my word. For think not, I pray you, that my writing is of less account than my coming; for as I spoke when present, so now I write also when absent." Seest thou his fraternal solicitude? Seest thou forethought becoming a teacher? …

Homily 29 on 2 Corinthians ↗

Theophylact of Ohrid

I previously told you, and I say again: as during my second visit, being with you, I said, so now also through this epistle I declare to you — to those who have sinned, as being in need of correction, and to the rest, as witnesses — that when I come again, I will not spare. He did not say: I will punish, but used the fatherly word of sparing; for if I find them, he says, uncorrected, then I will not delay for long.

Commentary on 2 Corinthians ↗

Cyprian

That all sins may be forgiven him who has turned to God with his whole heart... Also in the same [second Epistle of the blessed Paul to the Corinthians]: "I told you before, and foretell you as I sit present; and absent now from those who before have sinned, and to all others; as, ill shall come again, I will not spare."

Pseudo-Cyprian Exhortation to Repentance ↗

Thomas Aquinas

But he threatens a severe sentence, saying: I warned those who sinned before and all the others. Here he first suggests the judicial process to be followed, which requires that three warnings have been given. In regard to this he says: I have warned you before twice, as I warned them when present, namely, when I was among you, so I warn them now, that is, while absent. Thus he warns them three times. I warn, I say, those who sinned before and all the others. As if to say: I warn everyone. …

Commentary on 2 Corinthians ↗