Although I recommend reading the whole document, at least take a look at these two quotes, and maybe just do a “Find Text” in it on the word “death” and another one on the word “tomb”.
17. In the liturgical books which deal with the feast either of the dormition or of the Assumption of the Blessed Virgin there are expressions that agree in testifying that, when the Virgin Mother of God passed from this earthly exile to heaven, what happened to her sacred body was, by the decree of divine Providence, in keeping with the dignity of the Mother of the Word Incarnate, and with the other privileges she had been accorded. Thus, to cite an illustrious example, this is set forth in that sacramentary which Adrian I, our predecessor of immortal memory, sent to the Emperor Charlemagne. These words are found in this volume: "Venerable to us, O Lord, is the festivity of this day on which the holy Mother of God suffered temporal death, but still could not be kept down by the bonds of death, who has begotten your Son our Lord incarnate from herself." (Sacramentarium Gregorianum)Some may not be familiar with the term dormition, which the soon to be beatified (I hope) Franciscan pope that guided us through the scourges of the Second World War equated with the term assumption. It may be Greek to you (it's actually Latin), but I suggest looking into it. Start where everyone else does nowadays: Wikipedia.
22. These words of St. John Damascene agree perfectly with what others have taught on this same subject. Statements no less clear and accurate are to be found in sermons delivered by Fathers of an earlier time or of the same period, particularly on the occasion of this feast. And so, to cite some other examples, St. Germanus of Constantinople considered the fact that the body of Mary, the virgin Mother of God, was incorrupt and had been taken up into heaven to be in keeping, not only with her divine motherhood, but also with the special holiness of her virginal body. "You are she who, as it is written, appears in beauty, and your virginal body is all holy, all chaste, entirely the dwelling place of God, so that it is henceforth completely exempt from dissolution into dust. Though still human, it is changed into the heavenly life of incorruptibility, truly living and glorious, undamaged and sharing in perfect life."(18) And another very ancient writer asserts: "As the most glorious Mother of Christ, our Savior and God and the giver of life and immortality, has been endowed with life by him, she has received an eternal incorruptibility of the body together with him who has raised her up from the tomb and has taken her up to himself in a way known only to him." (The Encomium in Dormitionem Sanctissimae Dominae Nostrate Deiparae Semperque Virginis Mariae, attributed to St. Modestus of Jerusalem, n. 14.)
Mary, the Mother of the Church, as pronounced by Venerable Pope Paul VI at the closing of the Second Vatican Council, died. But how could the sinless virgin die? Some say in imitation of her Son, but I am coming to understand that it was not in imitation, but because of her Son.
What follows is my own understanding based on some reading, much reflection and even more prayer. I could be wrong, and I leave it up to someone much wiser than me and with more authority to decide. Perhaps someone much wiser has already spoken on this, but I am ignorant of it. I am rather ignorant of much, but this seems most reasonable and purposeful to me, and fills me with great faith.
The mystery of our faith, the mystérium fídei, is the miracle of the Mass (or Divine Liturgy) veiled in the theological term transubstantiation. The Latin word mystérium comes from the Greek word μυστήριον, which St. Paul uses in Ephesians 5:32 (look it up in a couple of translations, such as the Douay-Rheims (this webpage also has the Greek and Latin) and either the New American Bible, the Jerusalem Bible (it's be nice if this one was online) or the RSV). St. Jerome translated this into Latin as sacramentum (although the Nova Vulgata has changed it to mysterium). The natural sacrament of the Church is marriage, which led to the supernatural sacrament of the Eucharist; both of which took place within the womb of the Spouse of the Holy Spirit at the time of the Incarnation. The Incarnation is both a marriage of God and man, and the transubstantiation of man (flesh and blood) into God.
It would take a small book to scratch the surface of what I briefly mentioned in the last paragraph, volumes to begin to explore and an eternity to try, but never come, to realize its full significance. This was the reason why, I believe, she, who is like God (מִיכָאֵל) and whose strength is God (גַּבְרִיאֵל), died.
Mary is the most perfect creature, but she is still a creature. She is like God, but she is infinitely not God. She has the most perfect understanding of the Word made Flesh, but that understanding is not the Word of God (Ὁ Λόγος). Our intellect has limitations that can never reach the heights of deity, even the most perfect intellect of the Theotokos (Θεοτόκος). However, our intellect has even greater limitation in this time, χρόνος, that will not exist in the time to come, καιρός.
If given the understanding possible in the time to come (καιρός) in this time (χρόνος) we would immediately pass on to that time (καιρός). This is what I believe happened to Our Lady.
Our Lady’s alter christus, St. John the Beloved Disciple, place the Son in the mouth of His Mother one last time, in which she was given the greatest understanding of the mystérium fídei possible, which is impossible in χρόνος, causing the Κοίμησις Θεοτόκου (Dormition of the Mother of God).
I pray that I expire in such a holy manner. Amen.
הֵילֵל (Lucifer), who was the shining one, the light bearer, the morning star, said, “Non serviam,” (I will not serve), when it was revealed to him who he must serve because she would out shine him by bearing the Light of God. He became הַשָּׂטָן (Satan) by opposing her who is the answer to the question, “Who is like God?” (מִיכָאֵל (Michael)). The mystérium fídei was accomplished when she who is the answer to this question, the Shining One, the Light (God) Bearer (Θεοτόκος (Theotokos)) and the Morning Star, said, “God is my strength.” (גַּבְרִיאֵל (Gabriel)).