Litanies and the Mass of Rogation for this day are of ancient origin, except the Introit, which in early days was replaced by the Litany in processions. The feast of St. Mark is of much later origin. The pagan festival, Robigalia, occurred on April 25th; young people used to go across the Milvian bridge to sacrifice to Robigus who preserved grain from blight. The Christian procession formed at St. Lawrence in Lucina and went by the Flaminian Way over the same bridge, where the sign In hoc singo vinces appeared to Constantine. Then going along the Tiber, passing in back of Castel Sant Angelo entered St. Peter’s. The people were thus taught that it was not the favor of the heathen god, but a devout life, humble prayer, and the intercession of the saints, especially that of St. Peter, the Pastor ovium, which would disarm the justice of God offended by our sins. This rite is called the Greater Litanies, because it was of a much more solemn nature than the ordinary stational litanies.
During the Procession, the Litany of the Saints is sung, followed by several Versicles and Prayers. The procession is a survival of classical tradition incorporated into religious customs; the Church preferred to give a spiritual significance to observances implanted in the hearts of the people, rather than suppress them partially. The Litany still preserves the very ancient type of prayer which ended the night vigil and served as a transition between the vigil office and the offering of the Holy Sacrifice. The oldest part of the Litany is that which begins with the words “Through the mystery of thy holy incarnation” which belongs to primitive Christianity.
The whole Mass shows us how highly we should value prayer. Even in the middle of the night, and even to the extent of seeming importunate, our prayers should rise to God, because our miseries and our weaknesses are so numerous, and because God has decreed that His grace shall be granted to us only on the wings of prayer.