John Chrysostom

"For even when we were come into Macedonia, our flesh had no relief." For since he said, "our tribulation;" he both explains of what sort it was, and magnifies it by his words, in order to show that the consolation and joys received from them was great, seeing it had repelled so great a sorrow. "But we were afflicted on every side." How on every side? for "without were fightings," from the unbelievers; "within were fears;" because of the weak among the believers, lest they should be drawn aside. …

Homily 14 on 2 Corinthians ↗

Theophylact of Ohrid

He speaks of his sorrow and describes it in strong terms, in order to show how great was the joy from them, since it drove away even such sorrow. He well said that the "flesh" had no rest; for the soul of Paul was unconquerable. "Attacks" from unbelievers. Because among the faithful there are weak ones who could be led astray by false brethren.

Commentary on 2 Corinthians ↗

Thomas Aquinas

Then when he says, For even when we came, he explains his commendation. But he said that he experienced two things, namely, joy and tribulation. First, therefore, he makes manifest his tribulation; secondly, his consolation (v. 6). He enlarges upon his tribulations for two reasons, namely, because the cure was removed, and because the tribulations were multiplied. Because of the removal of the cure he says: For even when we came, etc. …

Commentary on 2 Corinthians ↗