The celebration of Corpus Christi can be traced to 1208 when a sixteen-year old orphan named Juliana received a vision. Raised by the Augustinian nuns of Cornillion the young novice while at prayer saw the moon, whose disk was darkened in one area.
Years later the Holy Spirit blessed her with the interpretation of her vision. The moon was the Church. The darkened area a missing feast, required to complete the glory of the liturgical year.
Juliana confided her vision to her superiors, but not her inspired explanation, not for another eighteen years.
One of the people that she finally revealed it to was the archdeacon of Liege, Jacques Pantaleon. In 1261 he became Pope Urban IV, two years after her death in 1258. In 1264 Urban made Corpus Christi a feast of the universal Church.
The establishment of a new feast required that a new office be created for it, a selection of psalms, readings, etc. for use in the Mass and the Divine Office. Urban asked the brilliant Dominican scholar Thomas Aquinas to compose the office. The Hymn St. Thomas composed for use at Vespers is still sung today. It was the Pange Lingua:
- Pange, lingua, gloriosi Corporis mysterium...
- Sing my tongue the Saviors Glory, of His flesh the mystery sing;