1 Corinthians 14:9-19

9So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air. 10There are, it may be, so many kinds of voices in the world, and none of them is without signification. 11Therefore if I know not the meaning of the voice, I shall be unto him that speaketh a barbarian, and he that speaketh shall be a barbarian unto me.

12Even so ye, forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the Assembly. 13Wherefore let him that speaketh in an unknown tongue pray that he may interpret. 14For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful. 15What is it then? I will pray with the spirit, and I will pray with the understanding also: I will sing with the spirit, and I will sing with the understanding also. 16Else when thou shalt bless with the spirit, how shall he that occupieth the room of the unlearned say Amen at thy giving of thanks, seeing he understandeth not what thou sayest? 17For thou verily givest thanks well, but the other is not edified. 18I thank my God, I speak with tongues more than ye all: 19Yet in the Assembly I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue.