1 Corinthians 14:7-9

New King James Version

⁷ 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? ⁸ For if the trumpet makes an uncertain sound, who will prepare for battle? ⁹ 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.