1 Corinthians 14:1, 4, 22

Let love be your highest goal! But you should also desire the special abilities the Spirit gives—especially the ability to prophesy.

A person who speaks in tongues is strengthened personally, but one who speaks a word of prophecy strengthens the entire church.

So 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.