So andyc has not posted a video of him preaching to Sudanese where they understand him in their own tongue, and I hear it in English?
11 Cretans and Arabs—we hear them speaking in our own tongues the wonderful works of God.”
Therefore tongues are for a sign, not to those who believe but to unbelievers; but prophesying is not for unbelievers but for those who believe.
OK for a third time, lets educate you ignoramuses.
Paul said in verse 23 - "if the whole church comes together in one place, and all speak with tongues, and there come in those who are uninformed or unbelievers, will they not say that you are out of your mind?"
And so speaking in tongues is negative where unbelievers are concerned. It's the same issue that the 120 had when they all spoke in tongues on the day of Pentecost. No one was impressed, they all mocked.
And so when Paul states that tongues are a sign for unbelievers, he's talking about a negative sign. And this is the reason why people should not be speaking in tongues when there are unbelievers unless there is an interpretation.
Paul quotes Isaiah 28.....
11 For with stammering lips and another tongue He will speak to this people, 12 To whom He said, "This is the rest with which You may cause the weary to rest," And, "This is the refreshing"; Yet they would not hear. 13 But the word of the LORD was to them, "Precept upon precept, precept upon precept, Line upon line, line upon line, Here a little, there a little," That they might go and fall backward, and be broken And snared and caught.
Paul is quoting Isaiah to explain the fact that the Holy Spirit was to bring rest to those who accepted the word of God, but because the Israelites previously rejected the word, other tongues were a sign of judgement. The Assyrians and Babylonians speaking in other tongues were a sign that their unbelief was being judged.
This is why Paul told the church not to speak in another tongue in the church with unbelievers, because the negative sign to them was unnecessary, because the time was right for judgement.