1 Corinthians 14:9-11

9 So it is with you. Unless you speak intelligible words with your tongue, how will anyone know what you are saying? You will just be speaking into the air.

10 Undoubtedly there are all sorts of languages in the world, yet none of them is without meaning.

11 If then I do not grasp the meaning of what someone is saying, I am a foreigner to the speaker, and he is a foreigner to me.