John Chrysostom

Again even in this his apology he makes what he says more terrible, showing that it is not himself who is to punish, but God; for he added, "according to the authority which the Lord gave me;" and again, to show that he desires not to use his power to their punishment, he added, "not for casting down, but for building up." And he hinted indeed this now, as I said, but he left it to them to draw the conclusion that if they should continue unamended, even this again is building up, to punish those that are of such a mind. …

Homily 30 on 2 Corinthians ↗

Theophylact of Ohrid

Having greatly frightened them and put forth threats, he now presents a justification for this. I wrote thus because I desire that the threats and severity remain only in writing and not be carried out in reality; for I will certainly punish those who have not corrected themselves, since the Lord gave me authority. By this he shows that through him the Lord Himself punishes. …

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then, having given the admonition, he assigns the reason for it, saying, I write this while I am away from you, in order that when I come I may not have to be severe, i.e., I write these things to you in my absence to warn you, lest I be forced to do something against my will, which is that I may do nothing severe against you, except to the extent that I am compelled by you. …

Commentary on 2 Corinthians ↗