The Catholic Church teaches as dogma that the Virgin Mary "having completed the course of her earthly life, was assumed body and soul into heavenly glory". This doctrine was dogmatically defined by Pope Pius XII on 1 November 1950, in the apostolic constitution Munificentissimus Deus by exercising papal infallibility. While the Catholic Church and Eastern Orthodox Church believe in the Dormition of the Theotokos, which is the same as the Assumption, whether Mary had a physical death has not been dogmatically defined.
In Munificentissimus Deus (item 39) Pope Pius XII pointed to the Book of Genesis (3:15) as scriptural support for the dogma in terms of Mary's victory over sin and death as also reflected in 1 Corinthians 15:54: "then shall come to pass the saying that is written, Death is swallowed up in victory".
In the churches that observe it, the Assumption is a major feast day, commonly celebrated on 15 August. In many countries, the feast is also marked as a Holy Day of Obligation in the Roman Catholic Church and as a festival (under various names) in the Anglican Communion.
The Assumption (Latin: assumptio, "a taking") was defined as dogma by the Catholic Church in 1950, when Pope Pius XII defined it ex cathedra in his Apostolic Constitution Munificentissimus Deus. The Catholic Church itself interprets chapter 12 of the Book of Revelation as referring to it. The earliest known narrative is the so-called Liber Requiei Mariae (The Book of Mary's Repose), which survives intact only in an Ethiopic translation. Probably composed by the 4th century, this Christian apocryphal narrative may be as early as the 3rd century. Also quite early are the very different traditions of the "Six Books" Dormition narratives. The earliest versions of this apocryphon are preserved in several Syriac manuscripts of the 5th and 6th centuries, although the text itself probably belongs to the 4th century.
Later apocrypha based on these earlier texts include the De Obitu S. Dominae, attributed to St. John, a work probably from around the turn of the 6th century that is a summary of the "Six Books" narrative. The story also appears in De Transitu Virginis, a late 5th-century work ascribed to St. Melito of Sardis that presents a theologically redacted summary of the traditions in the Liber Requiei Mariae. The Transitus Mariae tells the story of the apostles being transported by white clouds to the deathbed of Mary, each from the town where he was preaching at the hour. The Decretum Gelasianum in the 490s declared some transitus Mariae literature apocryphal.