1 Corinthians 14:17

For thou verily givest thanks well, but the other is not edified. [The one who was so under the influence of the Spirit of God as to speak with tongues, produced words and sentences with little or no intellectual effort. His spirit, being in accord with the Spirit of God, uttered the exhortation or the prayer with his spirit rather than with his understanding. Therefore, taking the case of prayer as an example, Paul advises that the understanding be kept as active as the spirit, and that a man so control the flow of prayer as to pause from time to time that he might interpret it, thus making his understanding as fruitful as his spirit. If he does not do this, he prays with his tongue indeed, but his understanding bears no fruit in the congregation where he prays. For this reason the apostle made it his rule to pray with his spirit and interpret with his understanding, and to sing also in like manner. If the speaker did not do this, how could one who was not gifted to interpret say Amen to the petition offered, seeing that he knew not what it was? Thus, no matter how ably the gifted one might pray, the ungifted one would not be edified. Amen was then, as now, the word of ratification or assent to an expression of prayer or praise, of blessing or cursing (Deuteronomy 27:15; Nehemiah 5:13; Revelation 5:14). Justin Martyr (Ap., c. 65, 67) describes the use of the Amen, after the prayer at the communion service. It is to that or some similar use that Paul refers. Doddridge justly says that this passage is decisive against the ridiculous practice of the church of Rome of praying and praising in Latin, which is not only a foreign, but a dead, tongue. Moreover, it shows that prayer is not a vicarious duty done for us by others. We must join in it.]