According to the belief of Christians of the Roman Catholic Church, the Eastern Catholic Churches, the Eastern Orthodox Churches, Oriental Orthodoxy, and the Anglican Communion, the Assumption of Mary was the bodily taking up of the Virgin Mary into Heaven at the end of her life. The Roman 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 and infallibly defined by Pope Pius XII on November 1, 1950 in his Apostolic Constitution Munificentissimus Deus. This belief is known as the Dormition of the Theotokos by the Eastern and Oriental Orthodox Churches. In the churches which observe it, the Assumption is a major feast day, commonly celebrated on August 15. In many countries it is a Catholic Holy Day of Obligation
Although the Assumption (Latin: assūmptiō, "taken up") was only relatively recently defined as infallible dogma by the Catholic Church, and in spite of a statement by Saint Epiphanius of Salamis in AD 377 that no one knew whether Mary had died or not,  apocryphal accounts of the assumption of Mary into heaven have circulated since at least the 4th century. 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 by 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.
An Armenian letter attributed to Dionysus the Areopagite also mentions the event, although this is a much later work, written sometime after the 6th century. John of Damascus, from this period, is the first church authority to advocate the doctrine under his own name; he had been brought up in an environment in which a corporeal ascent of Muhammed into heaven was official policy, since he, and his father before him, held the post of imperial chancellor of the Islamic empire of the Umayyads, and Muhammed’s ascent into heaven is the subject of The Night Journey, a Surah in the Quran. His contemporaries, Gregory of Tours and Modestus of Jerusalem, helped promote the concept to the wider church.
In some versions of the story the event is said to have taken place in Ephesus, in the House of the Virgin Mary, although this is a much more recent and localized tradition. The earliest traditions all locate the end of Mary’s life in Jerusalem (see "Mary’s Tomb"). By the 7th century a variation emerged, according to which one of the apostles, often identified as St Thomas, was not present at the death of Mary, but his late arrival precipitates a reopening of Mary’s tomb, which is found to be empty except for her grave clothes. In a later tradition, Mary drops her girdle down to the apostle from heaven as testament to the event.  This incident is depicted in many later paintings of the Assumption.
The taking of Mary into Heaven became an established teaching across the Eastern, Western, Coptic and Oriental churches from at least the late 7th Century, the festival date settling at August 15. Theological debate about the Assumption continued, following the Reformation, climaxing in 1950 when Pope Pius XII defined it as dogma for the Catholic Church.  The Catholic Church has not claimed that this doctrine is founded on the apocryphal accounts as having any authority, nor that the church bases its teaching about the Assumption on them, but rather on the historic teaching of the Church down the centuries, the scholastic arguments in favor of it, and its interpretations of biblical sources. However, Protestant theologians reject such arguments as semantics; that apocryphal accounts did in fact become the basis for such church teachings, which were then set forth as dogma. They cite the fact that the idea did not gain acceptance in the church until the sixth century, after Gregory of Tours accepted the apocryphal work "Transitus Beatae Mariae".  Catholic theologian Ludwig Ott stated, "The idea of the bodily assumption of Mary is first expressed in certain transitus-narratives of the fifth and sixth centuries…. The first Church author to speak of the bodily assumption of Mary, in association with an apocryphal transitus B.M.V., is St. Gregory of Tours."  The Catholic writer Eamon Duffy goes further, conceding that "there is, clearly, no historical evidence whatever for it.".  However, the Catholic Church has never asserted nor denied that its teaching is based on the apocryphal accounts. The Church documents are silent on this matter and instead rely upon other sources and arguments as the basis for the doctrine.
Antecedents in Judeo-Christian traditions
Jean Danielou in his classical study of Jewish Christian theology noted in reference to state of the blessed dead before the resurrection on the last day that "there is . . . and exception to this waiting of the just before they enter into blessedness; in some cases their entrance is put forward. This seems to be a strictly Jewish Christian teaching. In the Ascension of Isaiah the visionary sees ‘holy Abel and Enoch" already in the seventh heaven (IX, 8-9), and with their raiment of glory (IX, 9), that is to say, they have been brought to life. Resurrection is in fact a necessary condition for entry into this place. II Enoch shows the ascension of Enoch as a final entry into the highest heaven, which is the place of ultimate blessedness (LXVII, 2), whereas I Enoch only knows of a temporary ascension. Irenaeus ascribes the former doctrine to the Elders.  say that those who have been translated are taken to Paradise, and remain there until the final consummation of all things, being the first to enter upon incorruption’ (Adv.Haer.V,5:1)."  Danielou concludes "There is a clear distinction between the exceptional state of those who are already restored to life, and the common condition of the souls of the righteous, who wait in Sheol for the resurrection, but in a happy region of that place."  Danielou also noted in his study that when the original Jewish Christian community of Jerusalem was dispersed after 70 A.D., the majority of this community established itself in Syria, becoming a major influence of the development of the Syrian Christian traditions, the very area where we later first find references to the such a similar translation of the Virgin Mary to the state of ultimate blessedness.
- Duggan, Paul E. (1989). The Assumption Dogma: Some Reactions and Ecumenical Implications in the Thought of English-speaking Theologians. Emerson Press, Cleveland, Ohio
- Shoemaker, Stephen J. (2002, 2006). Ancient Traditions of the Virgin Mary’s Dormition and Assumption. Oxford University Press, Oxford. ISBN 0-19-921074-8