1 Corinthians 14:22-25

So then tongues are for a sign, not to those who believe but to unbelievers; but prophecy is for a sign, not to unbelievers but to those who believe. Therefore if the whole church assembles together and all speak in tongues, and ungifted men or unbelievers enter, will they not say that you are mad? But if all prophesy, and an unbeliever or an ungifted man enters, he is convicted by all, he is called to account by all; the secrets of his heart are disclosed; and so he will fall on his face and worship God, declaring that God is certainly among you.