“But there are also many other things which Jesus did;
which, if they were written every one,
Saint John, Apostle, Evangelist, and protector of the Blessed Virgin Mary tells us that not all of the works of the Lord are written in the pages of the Bible. So how do we know the things that are not written in Scripture? The Church (through the Council of Trent) holds that there are two fonts of revelation: The Sacred Scriptures, and the Sacred Traditions of the Church. The Assumption of the Blessed Virgin Mary, celebrated in today’s Mass, may be the best example we have of a doctrine revealed by God and conveyed to us only through Sacred Tradition.
The Assumption is not mentioned in any of the Books of the Bible, and seems to have been committed to writing no earlier than 180 A.D. by St. Melito, Bishop of Sardis, which is located in the western part of modern day Turkey, close to Ephesus, the city where Saint John first cared for the Blessed Virgin. In this writing, Melito claims to have been told of the Assumption by Saint John.
Melito tells us that in the second year after the Resurrection an Angel appeared to Mary at the home of her parents near Mount Olivet, bearing a shining palm branch, and prophesying her death within three days. On the third day an earthquake warned Saint John who was transported to the house to find Mary joyfully preparing for her death. John prayed (successfully) that the other Apostles might be brought to celebrate her burial with him, and they were all transported from the places of their missions. Not only the Apostles, but our Lord Himself came, accompanied by a great multitude of angels. Mary’s soul was given over to the temporary custody of Saint Michael, and the Apostles were directed to take her body to a sepulchre to the East of Jerusalem in the burial ground at the Valley of Jehoshaphat. Saint John, carrying the shining palm led the procession as the Apostles carried her body.
At the sepulchre they were met once again by our Lord and the Angels. Melito says that it was the decision of Peter and the Apostles that our Lord should take Mary body and soul to heaven. To which the Lord said:
Our Lord then promised the Apostles
And our Lord and His Blessed Virgin Mother were carried to heaven by the multitude of Angels.
Now, some will argue that Saint Melito’s was actually composed a bit later, and that the author could not have spoken with Saint John. This may be so, but it is of little consequence, for it is the universal tradition of the undivided Church that Mary was, indeed, not left to the corruption of the earth at the end of her life, but was taken to Heaven, body and soul.
On this day, throughout the world, in all of the Churches—Catholic and non-Catholic alike—where the Eucharistic renewal of the Sacrifice of the Cross is offered, and where Mary is honored as the Mother of God, this same feast of Mary’s Assumption is duly celebrated.
It is this constant Sacred Tradition which prompted the saintly Pope Pius XII to define the Assumption as a doctrine of the Faith:
… 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.
Finally, I like to remind all of our people that this Assumption into Heaven is proof positive that throughout all of her life, Mary persevered in the graces of her Immaculate Conception. Mary had free will, just as Adam and Eve had free will—Mary could have sinned, but chose not to sin. As such, she is our shining example that men and women—delivered from sin by the Sacraments of penance and strengthened by the Holy Eucharist—can exercise their free will and remain in God’s grace for the rest of their lives.
“O Mary conceived without sin,
 Fra Angelico, “Dormition of the Virgin, 1432 http://uploads2.wikiart.org/images/fra-angelico/dormition-of-the-virgin-1432.jpg
 Apostolic Constitution of Pope Pius XII, Munificentissimus Deus, defining the Dogma of the Assumption, November 1, 1950 http://www.vatican.va/holy_father/pius_xii/apost_constitutions/documents/hf_p-xii_apc_19501101_munificentissimus-deus_en.html