20 Brothers, do not be children in your thinking. Be infants in evil, but in your thinking be mature. 21 In the Law it is written, “By people 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.” 22 Thus tongues are a sign not for believers but for unbelievers, while prophecy is a sign not for unbelievers but for believers. 23 If, therefore, the whole church comes together and all speak in tongues, and outsiders or unbelievers enter, will they not say that you are out of your minds? 24 But if all prophesy, and an unbeliever or outsider enters, he is convicted by all, he is called to account by all, 25 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.

26 What then, brothers? When you come together, each one has a hymn, a lesson, a revelation, a tongue, or an interpretation. Let all things be done for building up. 27 If any speak in a tongue, let there be only two or at most three, and each in turn, and let someone interpret. 28 But if there is no one to interpret, let each of them keep silent in church and speak to himself and to God. (ESV)