John Chrysostom

"Or did I commit a sin in abasing myself that ye might be exalted?" What he says is this; "I lived in straitness;" for this is the force of "abasing myself." "Can you then lay this to my charge? and do ye therefore lift up yourselves against me, because I abased myself by begging, by enduring straits, by suffering, by hungering, that ye might be exalted?" And how were they exalted by his being in straits? …

Homily 23 on 2 Corinthians ↗

Theophylact of Ohrid

Did I sin, he says, by this, and can you accuse me and boast against me, that I abased myself, living on charity and enduring hunger, "that you might be exalted," that is, be established in the faith? For they were not scandalized (which constitutes their greatest accusation) by the fact that they would not have been established otherwise, had he not endured hunger. …

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then when he says, Did I commit a sin, he shows that he has done more than all the others; and this because he preached without payment. In regard to this he does two things. First, he states the fact; secondly, he assigns the reason of the fact (v. 11). In regard to the first he does two things. First, he shows the fact as to the past; secondly, as to the future (v. 9b). He shows the past fact in two ways: first in general, and second in particular (v. 7b). …

Commentary on 2 Corinthians ↗