I Corinthians 14:6-12

But now, brethren, if I come to you speaking with tongues, what shall I profit you unless I speak to you either by revelation, by knowledge, by prophesying, or by teaching? Even things without life, whether flute or harp, when they make a sound, unless they make a distinction in the sounds, how will it be known what is piped or played? For if the trumpet makes an uncertain sound, who will prepare for battle? So likewise you, unless you utter by the tongue words easy to understand, how will it be known what is spoken? For you will be speaking into the air. There are, it may be, so many kinds of languages in the world, and none of them is without significance. Therefore, if I do not know the meaning of the language, I shall be a foreigner to him who speaks, and he who speaks will be a foreigner to me. Even so you, since you are zealous for spiritual gifts, let it be for the edification of the church that you seek to excel.