1 Corinthians 14:11-15

Therefore 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.

Even so ye, forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the church.

Wherefore let him that speaketh in an unknown tongue pray that he may interpret.

For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful.

What 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.