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.
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.
St. Juvenal, who was Bishop of Jerusalem told the emperor “that Mary died in the presence of all the Apostles, but that her tomb, when opened upon the request of St. Thomas, was found empty; the Apostles concluded that the body was taken up to heaven,” the saint recorded.
Pope Pius Xll, in 1950, defined that Mary "after the completion of her earthly life...was assumed body and soul into the glory of Heaven." Her body wasn't allowed to corrupt nor was it allowed to remain in a tomb. Though there are claims by some cities about possessing her temporary tomb.
In the early Christian centuries relics of saints and those who gave their lives for the faith were jealously guarded and highly prized. Many cities claim the mortal remains of saints, both famous and little-known. But there are no records of Mary's bodily remains being venerated anywhere.
Immaculate Virgin, Mother of Jesus and our Mother, we believe in your triumphant assumption into heaven where the angels and saints acclaim you as Queen. We join them in praising you and bless the Lord who raised you above all creatures. With them we offer you our devotion and love. We are confident that you watch over our daily efforts and needs, and we take comfort from the faith in the coming resurrection. We look to you, our life, our sweetness, and our hope. After this earthly life, show us Jesus, the blest fruit of your womb, O kind, O loving, O sweet virgin Mary.
Pray for us, O holy Mother of God.