1 Corinthians 14:8-10

New Catholic Bible

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.

¹⁰ There are many different languages that are used in the world, and none of them is without meaning.