John Chrysostom

"Remember ye not, that when I was yet with you, I told you these things?" Seest thou that it is necessary continually to say the same things, and to enlarge upon them in the same words? For behold, they heard him saying these things when present, and again they had need to be reminded of them. …

Homily on 2 Thessalonians 3 ↗

Theophylact of Ohrid

From this it is clear that the apostle transmitted great mysteries to the Thessalonians, and not in writing. Do you see that it is necessary to constantly speak about the same thing, to persistently repeat the same words? Here they heard the apostle speaking about this when he was among them, and yet again they had need of confirmation. Nothing extraordinary am I saying, he says, but the same thing I have always said. The apostle somewhat shames the Thessalonians, saying: "do you not remember?" Have you forgotten so quickly?

Commentary on 2 Thessalonians ↗

Thomas Aquinas

Then when he says, "do you not remember", he shows that he is writing nothing new, as though to say: when I was with you long ago, I said this. "I do not write a new command for you, but an old command, which you have had from the beginning" (2 John 5); "as we are in word by epistles when absent, such also we will be indeed when present" (2 Cor 10:11).

Commentary on 2 Thessalonians ↗