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 14:16
14:16 Otherwise, if you are praising God with your spirit, how can someone without the gift 1 say “Amen” to your thanksgiving, since he does not know what you are saying?
1 Corinthians 14:21-22
14:21 It is written in the law: “By people with strange tongues and by the lips of strangersI will speak to this people, yet not even in this way will they listen to me,” 2 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.
1 tnGrk “how can someone who fills the place of the unlearned say ‘Amen.’”