1 Corinthians 14:2 - 2 For he who speaks in another language speaks not to men, but to God, for no one understands, but in the Spirit he speaks mysteries.
1 Corinthians 14:5 (WEB)
Now I desire to have you all to speak with other languages, but even more that you would prophesy. For he is greater who prophesies than he who speaks in other languages, unless he interprets, that the assembly may be built up.
6 But now, brothers,[a] if I come to you speaking with other languages, what would I profit you unless I speak to you either by way of revelation, or of knowledge, or of prophesying, or of teaching?
7 Even lifeless things that make a sound, whether pipe or harp, if they didn’t give a distinction in the sounds, how would it be known what is piped or harped?
1 Corinthians 14:9 (WEB) - 9 So also you, unless you uttered by the tongue words easy to understand, how would it be known what is spoken? For you would be speaking into the air.
1 Corinthians 14:11 (WEB) - 11 If then I don’t know the meaning of the language, I would be to him who speaks a foreigner, and he who speaks would be a foreigner to me.
1 Corinthians 14:15 (WEB)3
What should I do? I will pray in the spirit, and I will pray with the understanding also. I will sing with the spirit, and I will sing with the understanding also.
1 Corinthians 14:16 (WEB)
Otherwise, if you bless with the spirit, how will he who fills the place of the unlearned say "Amen" at your giving of thanks, seeing that he doesn't know what you say?
1 Corinthians 14:19 (WEB)
However, in the assembly I would rather speak five words with my understanding, that I might instruct others also, than ten thousand words I another language.