1 Corinthians 14:9-11

Revised Geneva Translation

⁹ So likewise you, by the tongue, unless you utter words that are understood, how shall it be known what is spoken? For you shall speak into the air.

¹⁰ There are, it may be, so many kinds of voices in the world, and none of them without significance.

¹¹ Unless, then, I know the miraculous power of the voice, I shall be to him who speaks a Barbarian, and he who speaks, shall be to me a Barbarian.