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.
And from this we see that the use of different languages shows how God deals with those who don’t believe, not with those who believe. And prophecy shows how God works through those who believe, not through unbelievers.
So ·the gift of speaking in different kinds of languages [or ecstatic utterance; L tongues] is a sign for unbelievers, not for believers [C tongues served as a warning of judgment and a call to repentance; see Acts 2:4, 21, 38–40]. And prophecy is for believers, not for unbelievers.
That means that tongues are a sign of God’s power, not for those who are unbelievers, but to those who already believe. Preaching the word of God, on the other hand, is a sign of God’s power to those who do not believe rather than to believers. So that, if at a full church meeting you are all speaking with tongues and men come in who are both uninstructed and without faith, will they not say that you are insane? But if you are preaching God’s word and such a man should come in to your meeting, he is convicted and challenged by your united speaking of the truth. His secrets are exposed and he will fall on his knees acknowledging God and saying that God is truly among you!
So you see that being able to “speak in tongues” is not a sign to God’s children concerning his power, but is a sign to the unsaved. However, prophecy (preaching the deep truths of God) is what the Christians need, and unbelievers aren’t yet ready for it.
To be perfectly frank, I’m getting exasperated with your infantile thinking. How long before you grow up and use your head—your adult head? It’s all right to have a childlike unfamiliarity with evil; a simple no is all that’s needed there. But there’s far more to saying yes to something. Only mature and well-exercised intelligence can save you from falling into gullibility. It’s written in Scripture that God said, In strange tongues and from the mouths of strangers I will preach to this people, but they’ll neither listen nor believe. So where does it get you, all this speaking in tongues no one understands? It doesn’t help believers, and it only gives unbelievers something to gawk at. Plain truth-speaking, on the other hand, goes straight to the heart of believers and doesn’t get in the way of unbelievers. If you come together as a congregation and some unbelieving outsiders walk in on you as you’re all praying in tongues, unintelligible to each other and to them, won’t they assume you’ve taken leave of your senses and get out of there as fast as they can? But if some unbelieving outsiders walk in on a service where people are speaking out God’s truth, the plain words will bring them up against the truth and probe their hearts. Before you know it, they’re going to be on their faces before God, recognizing that God is among you.
So then the leshonot (tongues) are for an ot (miraculous sign), not to the ones believing, the ma’aminim in Rebbe, Melech HaMoshiach, but an ot (miraculous sign) to the Apikorosim; but divrei hanevu’ah (words of prophecy) are not for the Apikorosim, but for the ones believing, the ma’aminim in Moshiach.
So then, tongues are a sign to people who do not believe God. They are not a sign to those who believe him. But speaking words from God like a prophet is a sign to those who believe. It is not a sign to those who do not believe.