9 So with yourselves, if with your tongue you utter speech that is not intelligible, how will anyone know what is said? For you will be speaking into the air. 10 There are doubtless many different languages in the world, and none is without meaning, 11 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. 12 So with yourselves, since you are eager for manifestations of the Spirit, strive to excel in building up the church. 13 Therefore, one who speaks in a tongue should pray for the power to interpret.
Matthew Henry's Commentary on 1 Corinthians 14:9-13
Commentary on 1 Corinthians 14:6-14
(Read 1 Corinthians 14:6-14)
Even an apostle could not edify, unless he spoke so as to be understood by his hearers. To speak words that have no meaning to those who hear them, is but speaking into the air. That cannot answer the end of speaking, which has no meaning; in this case, speaker and hearers are barbarians to each other. All religious services should be so performed in Christian assemblies, that all may join in, and profit by them. Language plain and easy to be understood, is the most proper for public worship, and other religious exercises. Every true follower of Christ will rather desire to do good to others, than to get a name for learning or fine speaking.