So it is with you. Unless you speak intelligible words with your tongue, how will anyone know what you are saying? You will just be speaking into the air.
In this paragraph he goes on to show how vain a thing the ostentation of speaking unknown and unintelligible language must be. It was altogether unedifying and unprofitable (Co1 14:6): If I come to you speaking with tongues, what will it profit you, unless I speak to you by revelation, or by knowledge, or by prophesying, or by doctrine?
Commenting on 1 Corinthians 14:6-14
So likewise you, unless ye utter by the tongue words easy to be understood,.... This is an accommodation of the foregoing similes to the case in hand: for as unless there is a distinction of notes and tunes, it cannot be music, nor it cannot be known what is piped or harped; and unless the trumpet gives a certain sound, none can know when to...
Verse 9. So likewise ye, etc. To apply the case. If you use a foreign language, how shall it be known what is said, or of what use will it be, unless it is made intelligible by interpretation? Utter by the tongue. Unless you speak. Words easy to be understood. Significant words, (margin;) words to which your auditors are accustomed. For ye shall speak into the air.