1 Corinthians 14:13-25
Therefore, he who speaks in a tongue should pray for the power to interpret. For if I pray in a tongue, my spirit prays but my mind is unfruitful. What am I to do? I will pray with the spirit and I will pray with the mind also; I will sing with the spirit and I will sing with the mind also. Otherwise, if you bless with the spirit, how can any one in the position of an outsider say the "Amen" to your thanksgiving when he does not know what you are saying? For you may give thanks well enough, but the other man is not edified. I thank God that I speak in tongues more than you all; nevertheless, in church I would rather speak five words with my mind, in order to instruct others, than ten thousand words in a tongue.
Brethren, do not be children in your thinking; be babes in evil, but in thinking be mature. In the law it is written, "By men of strange tongues and by the lips of foreigners will I speak to this people, and even then they will not listen to me, says the Lord." Thus, tongues are a sign not for believers but for unbelievers, while prophecy is not for unbelievers but for believers. If, therefore, the whole church assembles and all speak in tongues, and outsiders or unbelievers enter, will they not say that you are mad? But if all prophesy, and an unbeliever or outsider enters, he is convicted by all, he is called to account by all, the secrets of his heart are disclosed; and so, falling on his face, he will worship God and declare that God is really among you.