1 Corinthians 14:6-13

But now, brethren, if I come unto you speaking with tongues, what shall I profit you, unless I speak to you either by way of revelation, or of knowledge, or of prophesying, or of teaching? Even things without life, giving a voice, whether pipe or harp, if they give not a distinction in the sounds, how shall it be known what is piped or harped? For if the trumpet give an uncertain voice, who shall prepare himself for war? So also ye, unless ye utter by the tongue speech easy to be understood, how shall it be known what is spoken? for ye will be speaking into the air. There are, it may be, so many kinds of voices in the world, and no kind is without signification. If then I know not the meaning of the voice, I shall be to him that speaketh a barbarian, and he that speaketh will be a barbarian unto me. So also ye, since ye are zealous of spiritual gifts, seek that ye may abound unto the edifying of the church. Wherefore let him that speaketh in a tongue pray that he may interpret.