Tongues are for unbelievers, but the unbelievers when they hear tongues will think you are crazy? It seems to be saying the opposite of how it is translated into English.
Brothers and sisters, stop thinking like children. In regard to evil be infants, but in your thinking be adults. In the Law it is written:
“With other tongues
and through the lips of foreigners
I will speak to this people,
but even then they will not listen to me,
says the Lord.”
Tongues, then, are a sign, not for believers but for unbelievers; prophecy, however, is not for unbelievers but for believers. So if the whole church comes together and everyone speaks in tongues, and inquirers or unbelievers come in, will they not say that you are out of your mind? But if an unbeliever or an inquirer comes in while everyone is prophesying, they are convicted of sin and are brought under judgment by all, as the secrets of their hearts are laid bare. So they will fall down and worship God, exclaiming, “God is really among you!”
The only way this makes sense is to see it light of the Isaiah verse that Paul has just quoted. The context of the Isaiah verse is judgment on Israel. They had made a a mockery of the faith, and now God was going to bring judgment through the foreign nations. The Lord is going to bring to the people of Israel a foreign power, foreign tongue speakers as a form of judgment.
So when we get to the issues of tongues in v. 22, the “sign” for unbelievers is not a positive sign. It is a judgment. It shows a hard that is hardened and not open to the things of God. It is not “for” unbelievers in a positive sense. It is a sign of a hardened heart.
The contrast in this verse is prophecy. An unbeliever can come in and hear clear words of prophecy and his heart can be convicted of his sin. Then, perhaps, the unbeliever will repent.
What Paul is doing once again is comparing the value of tongues, that mean nothing to an unbeliever, and are actually a sign of their hardness of heart, compared to prophecy, which is superior. It is superior not because of value, but because it can reach the heart of the unbeliever in an intelligible way.
The whole message of Paul is the same–when you are worshiping in the body of Christ together with other believers, eagerly desire and practice the gifts that build up other people.