In this passage the apostle pursues the argument, and reasons from other topics; as,
I. Tongues, as the Corinthians used them, were rather a token of judgment from God than mercy to any people (Co1 14:21): In the law (that is, the Old Testament) it is written, With men of other tongues and other lips will I speak to this people; and yet for all this they will not hear me, saith the Lord, Isa 28:11. Compare Deu 28:46, Deu 28:49. To both these passages, it is thought, the apostle refers. Both are delivered by way of threatening, and one is supposed to interpret the other. The meaning in this view is that it is an evidence that a people are abandoned of God when he gives them up to this sort of instruction, to the discipline of those who speak in another language. And surely the apostle's discourse implies, "You should not be fond of the tokens of divine displeasure. God can have no gracious regards to those who are left merely to this sort of instruction, and taught in language which they cannot understand. They can never be benefited by such teaching as this; and, when they are left to it, it is a sad sign that God gives them over as past cure." And should Christians covet to be in such a state, or to bring the churches into it? Yet thus did the Corinthian preachers in effect, who would always deliver their inspirations in an unknown tongue.
II. Tongues were rather a sign to unbelievers than to believers, Co1 14:22. They were a spiritual gift, intended for the conviction and conversion of infidels, that they might be brought into the Christian church; but converts were to be built up in Christianity by profitable instructions in their own language. The gift of tongues was necessary to spread Christianity, and gather churches; it was proper and intended to convince unbelievers of that doctrine which Christians had already embraced; but prophesying, and interpreting scripture in their own language, were most for the edification of such as did already believe: so that speaking with tongues in Christians assemblies was altogether out of time and place; neither one nor the other was proper for it. Note, That gifts may be rightly used, it is proper to know the ends which they are intended to serve. To go about the conversion of infidels, as the apostles did, had been a vain undertaking without the gift of tongues, and the discovery of this gift; but, in an assembly of Christians already converted to the Christian faith, to make use and ostentation of this gift would be perfectly impertinent, because it would be of no advantage to the assembly; not for conviction of truth, because they had already embraced it; not for their edification, because they did not understand, and could not get benefit without understanding, what they heard.
III. The credit and reputation of their assemblies among unbelievers required them to prefer prophesying before speaking with tongues. For, 1. If, when they were all assembled for Christian worship, their ministers, or all employed in public worship, should talk unintelligible language, and infidels should drop in, they would conclude them to be mad, to be no better than a parcel of wild fanatics. Who in their right senses could carry on religious worship in such a manner? Or what sort of religion is that which leaves out sense and understanding? Would not this make Christianity ridiculous to a heathen, to hear the ministers of it pray, or preach, or perform any other religious exercise, in a language that neither he nor the assembly understood? Note, The Christian religion is a sober and reasonable thing in itself, and should not, by the ministers of it, be made to look wild or senseless. Those disgrace their religion, and vilify their own character, who do any thing that has this aspect. But, on the other hand, 2. If, instead of speaking with tongues, those who minister plainly interpret scripture, or preach, in language intelligible and proper, the great truths and rules of the gospel, a heathen or unlearned person, coming in, will probably be convinced, and become a convert to Christianity (Co1 14:24, Co1 14:25); his conscience will be touched, the secrets of his heart will be revealed to him, he will be condemned by the truth he hears, and so will be brought to confess his guilt, to pay his homage to God, and own that he is indeed among you, present in the assembly. Note, Scripture - truth, plainly and duly taught, has a marvellous aptness to awaken the conscience, and touch the heart. And is not this much more for the honour of our religion than that infidels should conclude the ministers of it a set of madmen, and their religious exercises only fits of frenzy? This last would at once cast contempt on them and their religion too. Instead of procuring applause for them, it would render them ridiculous, and involve their profession in the same censure: whereas prophesying would certainly edify the church, much better keep up their credit, and might probably convince and convert infidels who might occasionally hear them. Note, Religious exercises in Christian assemblies should be such as are fit to edify the faithful, and convince, affect, and convert unbelievers. The ministry was not instituted to make ostentation of gifts and parts, but to save souls.

Will they not say that ye are mad? - So they well might, finding a whole assembly of people talking languages which those who had most need of instruction could not understand.

But if all prophecy,.... That is, all that speak publicly in the church, not together, but in their order, one after another, as is hereafter directed:

and there come in one that believeth not, or one unlearned; an unbeliever that has only the knowledge of his mother tongue, in which prophesying or preaching is used:

he is convinced of all, he is judged of all; of all the prophets or preachers; they all reprove him, and detect his secret, as the Arabic version renders the words; and to the same purport the Ethiopic. This must be understood of such persons whom the Spirit of God, under, and by the ministry of the word, powerfully works upon; whose hearts he opens to receive the word, and to whom he effectually applies it; whom he convinces of sin, righteousness, and judgment, shows the evil of their hearts and ways, reproves their errors, convicts them of their mistakes, and informs their judgments, and condemns all their principles and practices which are not agreeably to the word of God.

whole . . . all . . . tongues--The more there are assembled, and the more that speak in unknown tongues, the more will the impression be conveyed to strangers "coming in" from curiosity ("unbelievers"), or even from a better motive ("unlearned"), that the whole body of worshippers is a mob of fanatical "madmen"; and that "the Church is like the company of builders of Babel after the confusion of tongues, or like the cause tried between two deaf men before a deaf judge, celebrated in the Greek epigram" [GROTIUS].

unlearned--having some degree of faith, but not gifts [BENGEL].