1 Corinthians 14:21-22

21In 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.” Isaiah 28:11,12 22Tongues, then, are a sign, not for believers but for unbelievers; prophecy, however, is not for unbelievers but for believers.