16 Otherwise, if you bless and render thanks with [your] spirit [thoroughly aroused by the Holy Spirit], how can anyone in the position of an outsider or he who is not gifted with [interpreting of unknown] tongues, say the Amen to your thanksgiving, since he does not know what you are saying? [I Chron. 16:36; Ps. 106:48.]
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.