1 Corinthians 14:9-11

9So 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. 10Undoubtedly there are all sorts of languages in the world, yet none of them is without meaning. 11If then I do not grasp the meaning of what someone is saying, I am a foreigner to the speaker, and the speaker is a foreigner to me.