This feast, a Holy Day of Obligation, celebrates the day that God assumed Mary, his mother, into heaven after her death and is the principal feast day of our Blessed Mother.
It is believed that when Mary died her body was not subjected to the usual process of physical decay but was “assumed” into heaven and reunited there with her soul. On November 1, 1950, in the Apostolic Constitution, Munificentissimus Deus, Pope Pius XII defined the Assumption of Mary to be a dogma of faith; he wrote, “When the course of her earthly life was finished…was assumed [taken up], body and soul, into the glory of heaven.”’ In 1968, Pope Pius VI reaffirmed this belief by stating that Mary “…received in anticipation the future lot of all the just.” This belief is echoed in the opening prayer of the Mass celebrated on this day which concludes with the petition, “May we see heaven as our final goal and come to share her glory.”
Since early Christianity Mary has been honored for being the “God Bearer.” To avoid confusion with other Marian feasts, the Byzantine emperor Maurice, in the year 600, declared this festival of Mary’s Dormition, or “falling asleep,” to be observed on August 15, the date of the dedication of the church of the Dormition in Jerusalem. It was adopted in Rome in the time of Theodore 1 (642-49).
This day is also known as Assumption Day, The Dormition of the Most Holy Mother of God or the Feast of the Assumption. In art, the assumption of Mary into heaven is depicted by her body being borne up to heaven by angels, in contrast to the ascension of Christ, who rises by his own power.