The Assumption of Mary was not officially declared to be an article of the Roman Catholic faith until 1950 by Pope Pius XII:
"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” (Munificentissimus Deus).
The Roman Catholic Catechism explains this dogma in the following manner:
"Finally the Immaculate Virgin, preserved free from all stain of original sin, when the course of her earthly life was finished, was taken up body and soul into heavenly glory, and exalted by the Lord as Queen over all things, so that she might be the more fully conformed to her Son, the Lord of lords and conqueror of sin and death." The Assumption of the Blessed Virgin is a singular participation in her Son's Resurrection and an anticipation of the resurrection of other Christians." (CCC #966)
Enoch (Genesis 5:24), Elijah (2 Kings 2:11), and Jesus (Acts 1:9) are people recorded in Scripture as being bodily assumed into heaven. There is no such reference for Mary. Why would this not be recorded in Scripture? Ludwig Ott, in his book titled Fundamentals of Catholic Dogma, p. 209–210, says:
"The idea of the bodily assumption of Mary is first expressed in certain transitus–narratives of the fifth and sixth centuries. Even though these are apocryphal they bear witness to the faith of the generation in which they were written despite their legendary clothing. The first Church author to speak of the bodily ascension of Mary, in association with an apocryphal transitus B.M.V., is St. Gregory of Tours’."
The Catholic Encyclopedia tells us that the first "authentic" references to the bodily assumption of Mary can be found in writings dated to the sixth through eight centuries:
“The belief in the corporeal assumption of Mary is founded on the apocryphal treatise De Obitu S. Dominae, bearing the name of St. John, which belongs however to the fourth or fifth century. It is also found in the book De Transitu Virginis, falsely ascribed to St. Melito of Sardis, and in a spurious letter attributed to St. Denis the Areopagite. If we consult genuine writings in the East, it is mentioned in the sermons of St. Andrew of Crete, St. John Damascene, St. Modestus of Jerusalem and others. In the West, St. Gregory of Tours (De gloria mart., I, iv) mentions it first. The sermons of St. Jerome and St. Augustine for this feast, however, are spurious.”
The Assumption of Mary itself is just an assumption based on pious legends. This Roman Catholic dogma is apocryphal in origin.