1 Corinthians 14:10-15

There are doubtless many different languages in the world, and none is without meaning, but if I do not know the meaning of the language, I will be a foreigner to the speaker and the speaker a foreigner to me. So with yourselves, since you are eager for manifestations of the Spirit, strive to excel in building up the church. Therefore, one who speaks in a tongue should pray that he may interpret. For if I pray in a tongue, my spirit prays but my mind is unfruitful. What am I to do? I will pray with my spirit, but I will pray with my mind also; I will sing praise with my spirit, but I will sing with my mind also.