1 Corinthians 14:8-12

For if the trumpet produces an indistinct sound, who will prepare himself for battle?

So you too, unless you produce intelligible speech by the tongue, how will it be known what is spoken? For you will just be talking to the air.

There are, perhaps, a great many kinds of languages in the world, and none is incapable of meaning.

So if I do not know the meaning of the language, I will be unintelligible to the one who speaks, and the one who speaks will be unintelligible to me.

So you too, since you are eager to possess spiritual gifts, strive to excel for the edification of the church.