1 Corinthians 14:22-24

22So that tongues are for a sign, not to those who believe, but to unbelievers; but prophecy, not to unbelievers, but to those who believe.

23If therefore the whole assembly come together in one place, and all speak with tongues, and simple [persons] enter in, or unbelievers, will not they say ye are mad?

24But if all prophesy, and some unbeliever or simple [person] come in, he is convicted of all, he is judged of all;