1 Corinthians 14:7-9

New Revised Standard Version Catholic Edition

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