1 Corinthians 14:21-22

It is written in the Law, “BY MEN OF STRANGE TONGUES AND BY THE LIPS OF FOREIGNERS I WILL SPEAK TO THIS PEOPLE, AND NOT EVEN THEN WILL THEY LISTEN TO ME,” says the Lord. [Is 28:11, 12] Therefore, [unknown] tongues are [meant] for a [supernatural] sign, not to believers but to unbelievers [who might be receptive]; while prophecy [foretelling the future, speaking a new message from God to the people] is not for unbelievers but for believers.