1 Corinthians 14:11-13

Young's Literal Translation

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;