1 Corinthians 14:9-11

Amplified Bible, Classic Edition

⁹ Just so it is with you; if you in the [unknown] tongue speak words that are not intelligible, how will anyone understand what you are saying? For you will be talking into empty space!

¹⁰ There are, I suppose, all these many [to us unknown] tongues in the world [somewhere], and none is destitute of [its own power of] expression and meaning.

¹¹ But if I do not know the force and significance of the speech (language), I shall seem to be a foreigner to the one who speaks [to me], and the speaker who addresses [me] will seem a foreigner to me.