John Chrysostom

Moreover as he has eagerly endeavored this, so is he desirous also to show that his mind was quite joined to them; wherefore also he added, "For we rejoice when we are weak, and ye are strong. For this also we pray for even your perfecting." "For most certainly," he says, "we cannot do any thing against the truth, that is, punish you if you are well pleasing [to God]; besides, because we cannot, we therefore do not wish it, and even desire the contrary. …

Homily 29 on 2 Corinthians ↗

Theophylact of Ohrid

These words show the apostle's strong devotion to the Corinthians, for the meaning of his words is as follows: do not think that I grieve because I cannot demonstrate my power over you in the event that you do not stumble. On the contrary, I am very glad when I myself am "weak," that is, am considered weak, as one who shows no power in punishing you, and when you are "strong," that is, virtuous and free from falls. …

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then when he says, For we are glad, he removes the false suspicion on account of the joy conceived over their good. First, he mentions the joy he conceives over their innocence; secondly, the prayer he utters for their perfection (v. 9b). He says therefore: we pray that you may appear approved, but we infirm; and this is clear from our emotion, because we rejoice that some among you are good and innocent, thus taking from us the power to judge and making us seem weak; and this is what he says: For we are glad when we are weak, i.e., …

Commentary on 2 Corinthians ↗