1 Corinthians 14:7-9

New Catholic Bible

⁷ Even inanimate things produce sound, such as a flute or a harp. If they do not produce distinct notes, how can anyone tell what tune is being played?

⁸ Or again, if the bugle call is unclear, who will get ready for battle? ⁹ Similarly, if you speak in tongues and your speech is unintelligible, how will anyone be able to understand what you are saying? For you will be talking to empty air.