1 Corinthians 14:7-9

Revised Standard Version

⁷ If even lifeless instruments, such as the flute or the harp, do not give distinct notes, how will any one know what is played? ⁸ And if the bugle gives an indistinct sound, who will get ready for battle? ⁹ So with yourselves; if you in a tongue utter speech that is not intelligible, how will any one know what is said? For you will be speaking into the air.