Fulfilled is all that David told
In true prophetic song of old;
How God the nations' King should be,
For God is reigning from the tree.
Vexilla Regis was written by Venantius Fortunatus (530-609) and is considered one of the greatest hymns of the liturgy. Fortunatus wrote it in honor of the arrival of a large relic of the True Cross which had been sent to Queen Radegunda by the Emperor Justin II and his Empress Sophia. Queen Radegunda had retired to a convent she had built near Poitiers and was seeking out relics for the church there. To help celebrate the arrival of the relic, the Queen asked Fortunatus to write a hymn for the procession of the relic to the church.
The True Cross is said to have been discovered in 326 by the mother of the Roman Emperor Constantine I, Helena of Constantinople, during a pilgrimage she made to Jerusalem. The Church of the Holy Sepulchre was then built at the site of the discovery, by order of Helena and Constantine. The church was dedicated nine years later, with a portion of the cross placed inside it.
The date of the feast marks the dedication of the Church of the Holy Sepulchre in 335
This was a two-day festival: although the actual consecration of the church was on September 13, the cross itself was brought outside the church on September 14 so that the clergy and faithful could pray before the True Cross, and all could come forward to venerate it.
Almighty God, whose Son our Savior Jesus Christ was lifted high upon the cross that he might draw the whole world unto himself: Mercifully grant that we, who glory in the mystery of our redemption, may have grace to take up our cross and follow him; who liveth and reigneth with thee and the Holy Ghost, one God, world without end. Amen.