John Chrysostom

"For the Son of God," saith he, "Who was preached among you by us, even by me, and Silvanus, and Timothy, was not yea and nay." For on this account he brings before them the company of the teachers also, as thence too giving credibility to the testimony by those who taught, and not who heard it only. And yet they were disciples; however in his modesty he counts them as in the rank of teachers. But what is, "was not yea and nay?" I have never, he saith, unsaid what before I said in the Preaching. …

Homily 3 on 2 Corinthians ↗

Theophylact of Ohrid

Finally he says what word was not "yes" and "no." He Whom we preached to you was not "yes" and "no," that is, one thing was not preached now and another thing now, but it was "yes," that is, what was preached was firm and without wavering. He also lists many of those who preached, presenting their testimony as worthy of belief and at the same time teaching humility, for he presents his disciples as co-teachers.

Commentary on 2 Corinthians ↗

Augustine of Hippo

And when we confess that we have lied, we speak that which is true; for we say what we know, for we know that we lied. But that Word which is God, and can do more than we, cannot do this. For it "can do nothing except what it sees the Father do;" and it "speaks not of itself," but it has from the Father all that it speaks, since the Father speaks it in a special way; and the great might of that Word is that it cannot lie, because there cannot be there "yea and nay," but "yea yea, nay nay." Well, but that is not even to be called a …

On The Trinity 15.15 ↗

Thomas Aquinas

In regard to the cause, he excuses himself for two reasons, namely, from the motive and the efficient cause. His motive for not lying is that a person who assumes an office is naturally moved to what suits that office and not to what is contrary; but it is obvious that the Apostle's office is to preach the truth. Therefore, he is not moved to the contrary of the truth, which is to lie. …

Commentary on 2 Corinthians ↗