1 Corinthians 14:23-28

23So then, if the whole church gathers together and all of you speak in [unknown] tongues, and outsiders or those who are not gifted [in spiritual matters] or unbelievers come in, will they not say that you are out of your mind?

24But if all prophesy [foretelling the future, speaking a new message from God to the people], and an unbeliever or outsider comes in, he is convicted [of his sins] by all, and he is called to account by all [because he can understand what is being said];

25the secrets of his heart are laid bare. And so, falling on his face, he will worship God, declaring that God is really among you.

26What then is the right course, believers? When you meet together, each one has a psalm, a teaching, a revelation (disclosure of special knowledge), a tongue, or an interpretation. Let everything be constructive and edifying and done for the good of all the church.

27If anyone speaks in a tongue, it should be limited to two or at the most three, and each one speaking in turn, and one must interpret [what is said].

28But if there is no one to interpret, the one [who wishes to speak in a tongue] must keep silent in church; let him speak to himself and to God.