You give thanks well, but the other is not edified.

Lest it be thought that the gift of tongues is decisively degrading, he says: "For your part, you give thanks well, but since there is no benefit to your neighbor, your thanksgiving is useless."

I thank my God, for I speak with tongues more than all of you.

Lest they think that he degrades this gift because he himself does not have it, he says: I speak with tongues more than anyone else.

But in church I would rather speak five words with my mind, in order to instruct others, than a thousand words in an unknown tongue.

By my mind, that is, by understanding and being aware of my own words, and being able to explain them in order to benefit others as well. Than a thousand words in an unknown tongue, that is, when I cannot interpret them; for in that case the benefit is limited to me alone. Five words are spoken by every teacher who applies a suitable medicine to each of our five senses.

Fraternity! Do not be children in mind: be infants in evil, but be of full age in mind.

Having shown the place of the gift of tongues, he finally uses terrible speech and reproaches them for philosophizing like children. For truly, it is characteristic of children to marvel at small things, because they can amaze as well as tongues, and despise great things, because they do not reveal anything new, such as prophecies. And so, here it convinces us not to be arrogant, even simply not to know what malice is, just as children do not know, but to be perfect in mind, that is, to reason which gifts are higher and more useful. And in other words: an infant is evil who does no harm to anyone, but is not malicious, like a child, and he is perfect in mind who, doing no harm to anyone, is still beneficial, and not only avoids evil, but also achieves virtue, and preserves himself unharmed from temporal things. This instruction is similar to the following: "Be ye wise as serpents, and simple as doves" (Matt. 10:16).

In the law it is written: "With other tongues and with other lips I will speak to this people; but even then they will not listen to Me, says the Lord.

Again he compares prophecy with tongues, and shows its superiority, and in what it is, is evident from what is said next. The entire Old Testament is usually called the Law. Wherefore even now he speaks of the words written at the end of the book of Isaiah (28:11,12) as being written in the law. With words, but even then they will not listen to Me, He shows that the miracle could amaze them, but if they are not convinced, then it is their fault. For God always does His own and manifests His providence, although He knows that men will not submit, that they may be unanswerable.

Thus, tongues are a sign, not for believers, but for unbelievers.

A sign amazes, but does not teach and does not benefit, and often harms, like a tongue without interpretation, which is why further (v. 23) it says, "Will it not be said that you are possessed?" Moreover, signs are given for unbelievers, for believers have no need of them, because they already believe.

Prophecy is not for unbelievers, but for believers.

Prophecy, he says, is beneficial to believers because it instructs them. But does prophecy not serve even for the faithful? How then (v. 24) does he say, if all prophesy, and any unbeliever will come in? This is a prophecy for unbelievers as well. To this it may be answered: The apostle did not say that prophecy is useless to unbelievers, but that it is not a useless sign, like tongues. In short: the tongue is a sign for unbelievers, that is, only for their amazement, and prophecy is useful to believers and unbelievers, rebuking them, although it is not called a sign for them.