Thematic Bible: Should not be made in an unknown language

For if I pray in a tongue, my spirit prays but my mind is unproductive. {Therefore what should I do}? I will pray with my spirit, but I will also pray with my mind. I will sing praise with my spirit, but I will also sing praise with my mind. For otherwise, if you praise in [your] spirit, how will the one who fills the place of the outsider say the "amen" at your thanksgiving, because he does not know what you are saying?