1 Corinthians 14:21-23

14:21 It is written in the law: “By people with strange tongues and by the lips of strangers I will speak to this people, yet not even in this way will they listen to me,” ¹  says the Lord. 14:22 So then, tongues are a sign not for believers but for unbelievers. Prophecy, however, is not for unbelievers but for believers. 14:23 So if the whole church comes together and all speak in tongues, and unbelievers or uninformed people enter, will they not say that you have lost your minds?

[14:21]  ¹ sn A quotation from Isa 28:11-12.