John Chrysostom

"But in every thing commending ourselves as ministers of God." This is far greater. For it is not the same thing to be free from accusation; and to exhibit such a character as in everything to appear "ministers of God." For neither is it the same thing to be quit of accusation, and to be covered with praises. And he said not appearing, but "commending," that is 'proving.' Then he mentions also whence they became such. Whence then was it? "In much patience" he says, laying the foundation of those good things. …

Homily 12 on 2 Corinthians ↗

Theophylact of Ohrid

This is much higher: not only to make oneself pure from accusations and reproaches, but also to show such a life that from it one can see that he is a servant of God. He did not say: we show ourselves, but "we commend ourselves," that is, we show ourselves to be such in deed. He also speaks of the manner in which they become such, that is, through patience, and not simply through patience, but through "great patience." For it is not enough to endure one particular affliction or two, but one must be patient to the end. …

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then when he says, but as servants of God we commend ourselves in every way, he teaches them how to use the grace they received for doing good. He says therefore: let us give no offense to anyone, but we commend ourselves, both you and we, in work and word and in all things which pertain to the virtues, such ministers of God as we ought to be, i.e., let us conform ourselves to God by doing his will: "Like the magistrate of the people, so are his officials" (Sir. …

Commentary on 2 Corinthians ↗