1 Corinthians 14:9-11

Young's Literal Translation

⁹ so also ye, if through the tongue, speech easily understood ye may not give -- how shall that which is spoken be known? for ye shall be speaking to air.

¹⁰ There are, it may be, so many kinds of voices in the world, and none of them is unmeaning,

¹¹ if, then, I do not know the power of the voice, I shall be to him who is speaking a foreigner, and he who is speaking, is to me a foreigner;