He who speaks in an [unknown] tongue edifies himself, but he who prophesies edifies the church.

In the law it is written: "With men of other tongues and by strange lips I will speak to this people; and yet not even in this way will they hear Me," says the Lord.

So then tongues are for a sign, not to those who believe but to unbelievers; but prophesying is not for unbelievers but for those who believe.