1 Corinthians 14:13 in the King James Version
Wherefore let him that speaketh in an unknown tongue pray that he may interpret.
Context
12 So also you, since you are zealous for spiritual gifts, seek that you may abound to the building up of the assembly.
13 Therefore let him who speaks in another language pray that he may interpret.
14 For if I pray in another language, my spirit prays, but my understanding is unfruitful.