1 Corinthians 14:9 in the King James Version
So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air.
Context
8 For if the trumpet gave an uncertain sound, who would prepare himself for war?
9 So also you, unless you uttered by the tongue words easy to understand, how would it be known what is spoken? For you would be speaking into the air.
10 There are, it may be, so many kinds of languages in the world, and none of them is without meaning.