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.

9. So … ye—who have life; as opposed to "things without life" (1Co 14:7).

by the tongue—the language which ye speak in.

ye shall speak—Ye will be speaking into the air, that is, in vain (1Co 9:26).