The reading is from St. Paul's First Letter to the Corinthians 14:6-19

Brethren, if I come to you speaking in tongues, how shall I benefit you unless I bring you some revelation or knowledge or prophecy or teaching? If even lifeless instruments, such as the flute or the harp, do not give distinct notes, how will any one know what is played? And if the bugle gives an indistinct sound, who will get ready for battle? So with yourselves; if you in a tongue utter speech that is not intelligible, how will any one know what is said? For you will be speaking into the air. There are doubtless many different languages in the world, and none is without meaning; but if I do not know the meaning of the language, I shall be a foreigner to the speaker and the speaker a foreigner to me. So with yourselves; since you are eager for manifestations of the Spirit, strive to excell in building up the church. Therefore, he who speaks in a tongue should pray for the power to interpret. For if I pray in a tongue, my spirit prays but my mind is unfruitful. What am I to do? I will pray with spirit and I will sing with the mind also. Otherwise, if you bless with the spirit, how can any one in the position of an outsider say the "Amen" to your thanksgiving when he does not know what you are saying? For you may give thanks well enough, but the other man is not edified. I thank God that I speak in tongues more than you all; nevertheless, in church I would rather speak five words with my mind, in order to instruct others, than ten thousand words in a tongue.