1 Corinthians 14:11 YLT

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;

¹²  so also ye, since ye are earnestly desirous of spiritual gifts, for the building up of the assembly seek that ye may abound;

¹³  wherefore he who is speaking in an 'unknown' tongue -- let him pray that he may interpret;