1 Corinthians 14:22-24

22Tongues, then, are a sign, not for believers but for unbelievers; prophecy, however, is not for unbelievers but for believers.

23So 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?

24But if an unbeliever or an inquirer comes in while everyone is prophesying, they are convicted of sin and are brought under judgment by all,