1 Corinthians 14:9-11

RKJNT(i) 9 So likewise you, unless you utter by the tongue words that are easy to understand, how shall it be known what is spoken? for you shall speak into the air. 10 There are, it may be, many kinds of languages in the world, and none of them is without meaning. 11 But if I do not know the meaning of the language, I shall be to him who speaks a foreigner, and he who speaks shall be a foreigner to me.