1 Corinthians 14:14

For if I pray with a tongue, my spirit is praying, but my mind is not fruitful.

For the one speaking with a tongue speaks not to men, but to God; for no one hears him; but he speaks mysteries in the spirit:

Then what is it? I will pray with my spirit, and I will pray with my mind also: I will sing with my spirit, and I will sing with my mind also.

but I would rather speak five words in the church with my understanding, so that I may indeed teach others, than ten thousand words in a tongue.

Treasury of Scripture Knowledge

For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful.

For the one speaking with a tongue speaks not to men, but to God; for no one hears him; but he speaks mysteries in the spirit: