1 Corinthians 14:13 KJV
Wherefore let him that speaketh in an unknown tongue pray that he may interpret.
1 Corinthians 14:13, King James Version
In context
12 Even so ye, forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the church.
13 Wherefore let him that speaketh in an unknown tongue pray that he may interpret.
14 For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful.