1 Corinthians 14:9-11

Modern English Version

⁹ So also you, unless with the tongue you speak words easy to understand, how will it be known what is spoken? For you shall speak into the air. ¹⁰ There are, it may be, so many kinds of languages in the world, and none of them is without significance. ¹¹ Therefore, if I do not know the meaning of the speech, I shall be a barbarian to him who speaks, and he who speaks will be a barbarian to me.