John Chrysostom

"Howbeit in the Church I had rather speak five words with my understanding, that I might instruct others also." What is that, "speak with my understanding, that I might instruct others also?" "Understanding what I say," and "words which I can both interpret to others, and speak intelligently, and teach the hearers. Than ten thousand words in a tongue." Wherefore? "That I may instruct others," saith he. For the one hath but display only; the other, great utility: this being what he everywhere seeks, I mean the common profit. …

Homily on 1 Corinthians 35 ↗

Theophylact of Ohrid

"With my mind," that is, understanding and being conscious of my words, and being able to explain them, so as to bring benefit to others as well. "Than ten thousand words in an unknown tongue," that is, when I cannot interpret them; for in such a case the benefit is limited to me alone. And "five words" are spoken by every teacher who applies the proper remedy to each of our five senses.

Commentary on 1 Corinthians ↗

Thomas Aquinas

Here he presents himself as an example. As if to say: If I have the gift of tongues, just as you, you should do as I do. But I would rather speak five words in the church, i.e., a few words, with my mind and understand and be understood, in order to instruct others than ten thousand, i.e., any number of words in a tongue; which is not to speak to the mind in any way, as explained above. Some say that he says, five, because the Apostle seems to prefer to say one prayer with understanding than many without understanding. …

Commentary on 1 Corinthians ↗