At the request of Pope Urban IV St. Thomas Aquinas (1225–1274) 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).
The hymn expresses the doctrine of transubstantiation, in which, according to the Roman Catholic faith, the bread and wine are changed into the Body and Blood of Christ.
Liturgical Use: Vespers hymn on the Feast of Corpus Christi: the Tangtum Ergo and doxology are sung during Benediction of the Blessed Sacrament. It is used also as a processional hymn on Holy Thursday, Corpus Christi, and during the Forty Hours’ Adoration.The Pange Lingua is pre-eminently the hymn of the Most Blessed Sacrament. It is the most beautiful of the great Eucharistic hymns of St. Thomas Aquinas.
Pange Lingua Gloriosi Hymn:
Translation by Father Caswall.