Optional Memorial (1969 Calendar): August 5
While each diocese and parish keeps its own dedication anniversary, the universal Church commemorates the consecration of the four great Roman basilicas, called the Major Basilicas: St. John Lateran, St. Peter, St. Paul Outside the Walls, and St. Mary Major.
Today we commemorate the Dedication of the Basilica of St. Mary Major. It is also called Liberian Basilica and Our Lady of the Snows, because of the miracle that occurred there. On the night of August 4-5 in the year 358 AD, snow began to fall on the location where St. Mary Major is located. This of course is a miracle considering it fell on that small location in the heat of August.
According to Tradition, the Virgin Mary appeared in a dream to two faithful Catholics, the patrician John and his wife, as well as to Pope Liberius (352-366), asking them to build a church in her honor where the snow would fall on the night of August 4-5. Pope Liberius went and traced the outlines of the church in the snow, and the first basilica was built on that site. However, it was completed nearly a century later by Pope Sixtus III (432-440) following the Council of Ephesus in 431 during which Mary was declared to be the Mother of God.
St. Mary Major is important to Christendom for three reasons:
(a) It stands as a venerable monument to the Council of Ephesus (431), at which the dogma of Mary's divine Motherhood was solemnly defined; the definition of the Council occasioned a most notable increase in the veneration paid to Mary.
(b) The basilica is Rome's "church of the crib," a kind of Bethlehem within the Eternal City; it also is a celebrated station church, serving, for instance, as the center for Rome's liturgy for the first Mass on Christmas. In some measure every picture of Mary with the divine Child is traceable to this church.
(c) St. Mary Major is Christendom's first Marian shrine for pilgrims. It set the precedent for the countless shrines where pilgrims gather to honor our Blessed Mother throughout the world. Here was introduced an authentic expression of popular piety that has been the source of untold blessings and graces for Christianity in the past as in the present.
Source: The Church's Year of Grace by Pius Parsch via Catholic Culture
Grant to us Thy servants, we beseech Thee, O Lord God, that we may enjoy perpetual health of mind and body: and through the intercession of blessed Mary ever Virgin may be delivered from present sorrow and possess eternal joy. Through our Lord.
Prayer Source: 1962 Roman Catholic Daily Missal