"Christ's faithful, through the teaching and the leadership of their pastors, have learned from the sacred books that the Virgin Mary, throughout the course of her earthly pilgrimage, led a life troubled by cares, hardships, and sorrows, and that, moreover, what the holy old man Simeon had foretold actually came to pass, that is, that a terribly sharp sword pierced her heart as she stood under the cross of her divine Son, our Redeemer. In the same way, it was not difficult for them to admit that the great Mother of God, like her only begotten Son, had actually passed from this life. But this in no way prevented them from believing and from professing openly that her sacred body had never been subject to the corruption of the tomb, and that the august tabernacle of the Divine Word had never been reduced to dust and ashes. Actually, enlightened by divine grace and moved by affection for her, God's Mother and our own dearest Mother, they have contemplated in an ever clearer light the wonderful harmony and order of those privileges which the most provident God has lavished upon this loving associate of our Redeemer, privileges which reach such an exalted plane that, except for her, nothing created by God other than the human nature of Jesus Christ has ever reached this level.
15. The innumerable temples which have been dedicated to the Virgin Mary assumed into heaven clearly attest this faith. So do those sacred images, exposed therein for the veneration of the faithful, which bring this unique triumph of the Blessed Virgin before the eyes of all men. Moreover, cities, dioceses, and individual regions have been placed under the special patronage and guardianship of the Virgin Mother of God assumed into heaven. In the same way, religious institutes, with the approval of the Church, have been founded and have taken their name from this privilege. Nor can we pass over in silence the fact that in the Rosary of Mary, the recitation of which this Apostolic See so urgently recommends, there is one mystery proposed for pious meditation which, as all know, deals with the Blessed Virgin's Assumption into heaven.
16. This belief of the sacred pastors and of Christ's faithful is universally manifested still more splendidly by the fact that, since ancient times, there have been both in the East and in the West solemn liturgical offices commemorating this privilege. The holy Fathers and Doctors of the Church have never failed to draw enlightenment from this fact since, as everyone knows, the sacred liturgy, "because it is the profession, subject to the supreme teaching authority within the Church, of heavenly truths, can supply proofs and testimonies of no small value for deciding a particular point of Christian doctrine.
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'.
18. What is here indicated in that sobriety characteristic of the Roman liturgy is presented more clearly and completely in other ancient liturgical books. To take one as an example, the Gallican sacramentary designates this privilege of Mary's as 'an ineffable mystery all the more worthy of praise as the Virgin's Assumption is something unique among men'. And, in the Byzantine liturgy, not only is the Virgin Mary's bodily Assumption connected time and time again with the dignity of the Mother of God, but also with the other privileges, and in particular with the virginal motherhood granted her by a singular decree of God's Providence. 'God, the King of the universe, has granted you favors that surpass nature. As he kept you a virgin in childbirth, thus he has kept your body incorrupt in the tomb and has glorified it by his divine act of transferring it from the tomb'.
19. The fact that the Apostolic See, which has inherited the function entrusted to the Prince of the Apostles, the function of confirming the brethren in the faith, has by its own authority, made the celebration of this feast ever more solemn, has certainly and effectively moved the attentive minds of the faithful to appreciate always more completely the magnitude of the mystery it commemorates. So it was that the Feast of the Assumption was elevated from the rank which it had occupied from the beginning among the other Marian feasts to be classed among the more solemn celebrations of the entire liturgical cycle. And, when our predecessor St. Sergius I prescribed what is known as the litany, or the stational procession, to be held on four Marian feasts, he specified together the Feasts of the Nativity, the Annunciation, the Purification, and the Dormition of the Virgin Mary. Again, St. Leo IV saw to it that the feast, which was already being celebrated under the title of the Assumption of the Blessed Mother of God, should be observed in even a more solemn way when he ordered a vigil to be held on the day before it and prescribed prayers to be recited after it until the octave day. When this had been done, he decided to take part himself in the celebration, in the midst of a great multitude of the faithful. Moreover, the fact that a holy fast had been ordered from ancient times for the day prior to the feast is made very evident by what our predecessor St. Nicholas I testifies in treating of the principal fasts which 'the Holy Roman Church has observed for a long time, and still observes'."
Munificentissimus Deus, Piux XII, 1 November 1950, Feast of All Saints.