This feast commemorates two events – the departure of Mary from this life and the assumption of her body into heaven. 

The Church’s official doctrine of the Assumption says that at the end of her life on earth Mary was assumed, body and soul, into heaven. 

The death or ‘Dormition’ of Mary is not recorded in the Christian canonical scriptures. Hippolytus of Thebes, a 7th- or 8th-century author, claims in his partially preserved chronology to the New Testament that Mary lived for 11 years after the death of Jesus. 

The term Dormition expresses the belief that the Virgin died without suffering, in a state of spiritual peace. This belief does not rest on any scriptural basis but is affirmed by Orthodox Christian Holy Tradition. It is testified to in some old Apocryphal writings, but neither the Orthodox Church nor other Christians regard these as possessing scriptural authority. 

Some mistakenly believe Mary “ascended” into heaven, which is incorrect according to the Bible. It was Jesus Christ who ascended into heaven, by his own power. But Mary was “assumed” or taken up into heaven by God. 

Observed as a holy day of obligation by Catholics and as a public holiday in some countries, devotees consider the Feast of the Assumption as the Holy Mother’s “heavenly birthday” and this is not a day of mourning for her loss, but a celebration of joy for the union of the mother with her beloved son. 

According to St. John of Damascus, the Roman Emperor Marcian requested the body of Mary, Mother of God at the Council of Chalcedon, in 451.