1 Corinthians 14:13-15

Young's Literal Translation

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

¹⁴ for if I pray in an [unknown] tongue, my spirit doth pray, and my understanding is unfruitful.

¹⁵ What then is it? I will pray with the spirit, and I will pray also with the understanding; I will sing psalms with the spirit, and I will sing psalms also with the understanding;