One of the memories about his mother centered around the "Tomb of Mary," close to Mount Zion, where the early Christian community had lived.
On the hill itself was the "Place of Dormition," the spot of Mary's "falling asleep," where she had died. At this time, the "Memory of Mary" was being celebrated.
Later it was to become our feast of the Assumption.
For a time, the "Memory of Mary" was marked only in Palestine, but then it was extended by the emperor to all the churches of the East.
The Assumption is the oldest feast day of Our Lady, but we don't know how it first came to be celebrated.
Its origin is lost in those days when Jerusalem was restored as a sacred city, at the time of the Roman Emperor Constantine (c. By then it had been a pagan city for two centuries, ever since Emperor Hadrian (76-138) had leveled it around the year 135 and rebuilt it as in honor of Jupiter.
In the seventh century, it began to be celebrated in Rome under the title of the "Falling Asleep" ("Dormitio") of the Mother of God.
Soon the name was changed to the "Assumption of Mary," since there was more to the feast than her dying.