1 Corinthians 14:22-25

Wherefore tongues are for a sign, not to them that believe, but to the unbelieving: but prophesying is for a sign, not to the unbelieving, but to them that believe. If therefore the whole church be assembled together and all speak with tongues, and there come in men unlearned or unbelieving, will they not say that ye are mad? But if all prophesy, and there come in one unbelieving or unlearned, he is reproved by all, he is judged by all; the secrets of his heart are made manifest; and so he will fall down on his face and worship God, declaring that God is among you indeed.