17. To be sure, you may give thanks well (nobly), but the bystander is not edified [it does him no good].
18. I thank God that I speak in [strange] tongues (languages) more than any of you or all of you put together;
19. Nevertheless, in public worship, I would rather say five words with my understanding and intelligently in order to instruct others, than ten thousand words in a [strange] tongue (language).
20. Brethren, do not be children [immature] in your thinking; continue to be babes in [matters of] evil, but in your minds be mature [men].
21. It is written in the Law, By men of strange languages and by the lips of foreigners will I speak to this people, and not even then will they listen to Me, says the Lord. [Isa. 28:11, 12.]
22. Thus [unknown] tongues are meant for a [supernatural] sign, not for believers but for unbelievers [on the point of believing], while prophecy (inspired preaching and teaching, interpreting the divine will and purpose) is not for unbelievers [on the point of believing] but for believers.
23. Therefore, if the whole church assembles and all of you speak in [unknown] tongues, and the ungifted and uninitiated or unbelievers come in, will they not say that you are demented?