1 Corinthians 14:21-22

21It is written in the Scriptures: “I will speak to my own people through strange languages and through the lips of foreigners. But even then, they will not listen to me,” says the Lord.

22So you see that speaking in tongues is a sign, not for believers, but for unbelievers. Prophecy, however, is for the benefit of believers, not unbelievers.