2 For if you have the ability to speak in tongues, you will be talking only to God, since people won't be able to understand you. You will be speaking by the power of the Spirit, but it will all be mysterious. 3 But one who prophesies strengthens others, encourages them, and comforts them. 4 A person who speaks in tongues is strengthened personally, but one who speaks a word of prophecy strengthens the entire church.
Matthew Henry's Commentary on 1 Corinthians 14:2-4
Commentary on 1 Corinthians 14:1-5
(Read 1 Corinthians 14:1-5)
Prophesying, that is, explaining Scripture, is compared with speaking with tongues. This drew attention, more than the plain interpretation of Scripture; it gratified pride more, but promoted the purposes of Christian charity less; it would not equally do good to the souls of men. What cannot be understood, never can edify. No advantage can be reaped from the most excellent discourses, if delivered in language such as the hearers cannot speak or understand. Every ability or possession is valuable in proportion to its usefulness. Even fervent, spiritual affection must be governed by the exercise of the understanding, else men will disgrace the truths they profess to promote.