1 Corinthians 14:9-11 Revised Geneva Translation (RGT)
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.