1 Corinthians 14:5-9

Now I wish that all of you spoke in unknown tongues, but even more [I wish] that you would prophesy. The one who prophesies is greater [and more useful] than the one who speaks in tongues, unless he translates or explains [what he says], so that the church may be edified [instructed, improved, strengthened]. Now, believers, if I come to you speaking in unknown tongues, how will I benefit you unless I also speak to you [clearly] either by revelation [revealing God’s mystery], or by knowledge [teaching about God], or by prophecy [foretelling the future, speaking a new message from God to the people], or by instruction [teaching precepts that develop spiritual maturity]? Yet even lifeless things, whether flute or harp, when producing a sound, if they do not produce distinct [musical] tones, how will anyone [listening] know what is piped or played? And if the [war] bugle produces an indistinct sound, who will prepare himself for battle? So it is with you, if you speak words [in an unknown tongue] that are not intelligible and clear, how will anyone understand what you are saying? You will be talking into the air [wasting your breath]!