1 Corinthians 14:22-25

Tongues, then, are a sign, not for believers but for unbelievers; prophecy, however, is not for unbelievers but for believers. So if the whole church comes together and everyone speaks in tongues, and inquirers or unbelievers come in, will they not say that you are out of your mind? But if an unbeliever or an inquirer comes in while everyone is prophesying, they are convicted of sin and are brought under judgment by all, as the secrets of their hearts are laid bare. So they will fall down and worship God, exclaiming, “God is really among you!”