1 Corinthians 14:9-11

New Catholic Bible

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. ¹¹ But if I do not comprehend the meaning of the language, I will be a foreigner to the speaker and he will be a foreigner to me.