1 Corinthians 14:22

22So thenὥστεαἱtonguesγλῶσσαιforεἰςa signσημεῖόνareεἰσινnotοὐto thoseτοῖςbelievingπιστεύουσινbutἀλλὰto theτοῖςunbelievingἀπίστοις,ἡbutδὲprophecyπροφητεία[is] notοὐto theτοῖςunbelievingἀπίστοιςbutἀλλὰto theτοῖςbelievingπιστεύουσιν.

So then, tongues are for a sign, not to the believing, but to the unbelieving; but prophecy [is] not to the unbelieving, but to the believing.