This beautiful feast was inaugurated for the universal Church is 1264 AD. The circumstances that led to this are surrounded by coincidence. St. Juliana, a nun in the diocese of Liege, Belgium, had a vision of Our Lord requesting a feast in honor of the Blessed Sacrament.
When she revealed this request, many ridiculed her, including members of her own order and even Church theologians. But she did have one great advocate in Fr. Jacques Pantaleon, who was Archdeacon of Liege. Through his efforts the feast began to be celebrated in that diocese.
Now comes the coincidence! This priest was appointed papal legate to Germany and later was installed as Patriarch of Jerusalem. The story does not stop there, for he was elected to the Chair of St. Peter as Pope Urban IV in 1261. Three years later he directed that the feast of Corpus Christi be celebrated throughout the whole Church.
Pope Urban commissioned the great Dominican scholar and theologian, St. Thomas Aquinas, to compose the texts for the Mass and the Divine Office for the new feast. The splendor, depth and devotion of the prayers and hymns of St. Thomas have enriched the liturgy with some of its most beautiful pieces. They are still sung today and admired for their profound spiritual meaning.
One of the hymns, Panis Angelicus (The Bread of Angels), is known and cherished widely, especially in the musical setting composed by Cesar Franck (1890). Another hymn by St. Thomas, Pange Lingua Gloriosi (Sing, my tongue, the Savior’s Glory), contains two stanzas, beginning with Tantum Ergo (Down in adoration falling), which are sung all over the world at every Benediction service. The best rendition of this music has remained the Gregorian chant. The last stanzas of another hymn by St. Thomas are also sung frequently at Benediction. The hymn is Verbum Supernum Prodiens (The Word from Heaven now Proceeding) and the section chosen from it begins with the words O Salutaris Hostia (O Saving Victim),
Then there is the sequence for the Mass: Lauda, Sion, Salvatorem (Praise, O Sion, your Redeemer), in which St. Thomas calls to mind in remarkable language the great truths of Christ’s revelation and the Church’s teaching about the Eucharist.
In addition, St. Thomas composed the Adoro Te Devote (Devoutly I adore you), and the verse: O Sacrum Convivium: O sacred banquet in which Christ is received: the memory of his Passion is recalled, the soul is filled with grace, and to us is given the pledge of future glory. Alleluia. (one can search on line for the texts of these hymns)