9 so also ye, if through the tongue, speech easily understood ye may not give—how shall that which is spoken be known? for ye shall be speaking to air. 10 There are, it may be, so many kinds of voices in the world, and none of them is unmeaning, 11 if, then, I do not know the power of the voice, I shall be to him who is speaking a foreigner, and he who is speaking, is to me a foreigner; 12 so also ye, since ye are earnestly desirous of spiritual gifts, for the building up of the assembly seek that ye may abound; 13 wherefore he who is speaking in an 'unknown' tongue—let him pray that he may 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.