At the request of Pope Urban IV, who extended the celebration of the Feast of Corpus Christi to the universal church, St. Thomas Aquinas composed the office (the official prayers of the Church) for the feast. This office is the source of the famous Eucharistic hymns "Pange Lingua Gloriosi" and "Tantum Ergo Sacramentum" (the final two verses of the "Pange Lingua").
Today, Catholics are familiar with the "Pange Lingua" primarily from its use during the procession at the Mass of the Lord's Supper on Holy Thursday evening, when the Body of Christ is removed from the tabernacle and transferred to another place to be kept overnight, while the altar is stripped bare.
This is a traditional English translation of the "Pange Lingua."
Sing, my tongue, the Savior's glory,
of His flesh the mystery sing;
of the Blood, all price exceeding,
shed by our immortal King,
destined, for the world's redemption,
from a noble womb to spring.
Of a pure and spotless Virgin
born for us on earth below,
He, as Man, with man conversing,
stayed, the seeds of truth to sow;
then He closed in solemn order
wondrously His life of woe.
On the night of that Last Supper,
seated with His chosen band,
He the Pascal victim eating,
first fulfills the Law's command;
then as Food to His Apostles
gives Himself with His own hand.
Word-made-Flesh, the bread of nature
by His word to Flesh He turns;
wine into His Blood He changes;
what though sense no change discerns?
Only be the heart in earnest,
faith her lesson quickly learns.
Down in adoration falling,
Lo! the sacred Host we hail;
Lo! o'er ancient forms departing,
newer rites of grace prevail;
faith for all defects supplying,
where the feeble senses fail.
To the everlasting Father,
and the Son who reigns on high,
with the Holy Ghost proceeding
forth from Each eternally,
be salvation, honor, blessing,
might and endless majesty. Amen.