1 Corinthians 14:2-11

14:2 For the one speaking in a tongue does not speak to people but to God, for no one understands; he is speaking mysteries by the Spirit. 14:3 But the one who prophesies speaks to people for their strengthening, encouragement, and consolation. 14:4 The one who speaks in a tongue builds himself up, but the one who prophesies builds up the church. 14:5 I wish you all spoke in tongues, but even more that you would prophesy. The one who prophesies is greater than the one who speaks in tongues, unless he interprets so that the church may be strengthened.

14:6 Now, brothers and sisters, if I come to you speaking in tongues, how will I help you unless I speak to you with a revelation or with knowledge or prophecy or teaching? 14:7 It is similar for lifeless things that make a sound, like a flute or harp. Unless they make a distinction in the notes, how can what is played on the flute or harp be understood? 14:8 If, for example, the trumpet makes an unclear sound, who will get ready for battle? 14:9 It is the same for you. If you do not speak clearly with your tongue, how will anyone know what is being said? For you will be speaking into the air. 14:10 There are probably many kinds of languages in the world, and none is without meaning. 14:11 If then I do not know the meaning of a language, I will be a foreigner to the speaker and the speaker a foreigner to me.

1 Corinthians 14:23

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?