The Assumption of the Blessed Virgin Mary
Admitted to the enjoyment of the delights of eternal contemplation, she chose at the feet of the Master the better part which shall not be taken away from her (Gospel, Communion). The Gospel of the Vigil was indeed formerly read after to-day's Gospel, in order to show that the Mother of Christ is happy among all others, because, better than all others, "she listened to the word of God". This word, the Word, the divine Wisdom which, under the Old Law, dwelt among the people of Israel (Epistle), dwelt in Mary under the New Law. The Word became incarnate in the womb of the Virgin, and now amid the splendour of the heavenly Sion He fills her with the delights of the beatific vision.
The Church on earth, like Martha, has to care for the necessities of this present life, but she also like her, invokes the help of Mary (Collect, Secret, Postcommunion).
A procession has always been a part of the feast of the Assumption. At Jerusalem it was formed by the numerous pilgrims who came to pray at the tomb of the Blessed Virgin and who thus contributed to the institution of this solemnity.
The clergy of Constantinople also held a procession on the feast of the Rest or Assumption of Mary. At Rome from the seventh to the sixteenth century the papal cortege, in which the representatives of the Senate and people took part, went on this day from the church of St. John Lateran to that of St. Mary Major. This ceremony was called the Litany.
On this occasion they used to recite over the people assembled for the procession the Collect for Assumption Day which is first in the Sacramentary and mentions this mystery, whilst our Collect of the Mass on August 15th was only the second Collect and has no direct relation to the feast. This is the first Collect: "It is our duty to honour the solemnity of this day, O Lord; the holy Mother of God did indeed suffer temporal death, although the bonds of this death could not hold back her whose flesh formed the body of Thy Son, our Lord who liveth and reigneth."
It is in the Basilica of St.Mary Major that the Station is held at Christmas to solemnize the mystery from which flowed all the glories of the Virgin, and it is also there that was solemnized the Assumption, in which they culminate. Mary received Jesus when He came to this world and it is Jesus who receives Mary into heaven.
Gaudeamus omnes in Domino, diem festum celebrantes sub honore beatae Mariae Virginis: de cujus Assumptione gaudent Angeli, et collaudant Filium Dei. Eructavit cor meum verbum bonum: dico ego opera mea Regi.
Let us all rejoice in the Lord, celebrating a festival-day in honour of the blessed Virgin Mary, for whose Assumption the angels rejoice and give praise to the Son of God. * My heart hath uttered a good word: I speak my works to the King.
(Psalm 44:2 from the introit of Mass)
Famulorum tuorum, quaesumus, Domine, delictis ignosce: ut, qui tibi placere de actibus nostris non valemus; Genitricis Filii tui Domini nostri intercessione salvemur.
Forgive, we beseech Thee, O Lord, the sins of Thy servants ; and may we, who are unable to please Thee by our deeds, be saved by the intercession of the Mother of Thy Son, our Lord.
Continuation of the holy Gospel according to St. Luke
At that time: Jesus entered into a certain town; and a certain woman, named Martha, received Him into her honse and she had a sister called Mary, who sitting also at the Lord's feet, heard His word. But Martha was busy about much serving : who stood and said: Lord, hast Thou no care that my sister hath left me alone to serve? Speak to her therefore, that she help me. And the Lord answering, said to her: Martha, Martha, thou art careful, and art troubled about many things: but one thing is necessary, Mary hath chosen the best part, which shall not be taken away from her.
(St Luke 10:38-42)
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/02006b.htm