Today is the feast of the Blessed Virgin Mary's Assumption, observed by Catholics and many other Christians. This important feast day commemorates the mother of Jesus Christ's physical and spiritual departure from this world when her body and soul were carried into God's presence.

Using papal infallibility, Venerable Pope Pius XII declared in 1950 that "the Immaculate Mother of God, the ever-Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory," confirming this belief about the Virgin Mary as the Church's timeless teaching.

The definition of the dogma in his Apostolic Constitution "Munificentissimus Deus" (Most Bountiful God) included the Pontiff's descriptions of numerous ancient customs that the Church has used to commemorate the Assumption over the ages.

The document also details the history of theological study on numerous Biblical texts that are interpreted as suggesting that Mary was assumed into heaven after her death, and it includes testimony on the topic from the early Church fathers.

While the biblical account of Mary's bodily assumption is unclear, Catholic tradition equates her to the “woman clothed with the sun” mentioned in the Book of Revelation's 12th chapter.

The woman is described in the verse as having "the moon under her feet, and on her head a crown of twelve stars," signifying that she is the mother of the Jewish Messiah. Her presence is described as "a great sign that appeared in heaven." As a result, this is how the Virgin Mary's ascension into heaven is frequently portrayed in Catholic artwork from the West.

Mary's ascension into heaven has also historically been considered a central tenet of Eastern Christianity. In defining her assumption, Pius XII referred to various early Byzantine liturgical sources and the eighth-century Arab Christian scholar St. John of Damascus.

In the calendar of Eastern Christianity, the same feast is observed on the same day, but it is usually called Mary's Dormition (falling asleep). A two-week period of fasting, like Lent, precedes the Eastern Catholic observance of the Dormition. The same fasting period was referenced by Pius XII in "Munificentissimus Deus" as being a part of the Western Christian tradition.

For both Roman and Eastern-rite Catholics, the feast of the Assumption is always a Holy Day of Obligation.