On this day the Word was made flesh and dwelt among us, uniting for evermore our human nature to the Divine nature. The Mystery of the Incarnation brings vividly before us the boundless condescension and humility of God the Son in stooping to our condition in order to be our Saviour. Equally it proclaims the glory and greatness of Mary, who was chosen to give to the Divine Word human flesh and human birth, and so to cooperate with God in the restoration of mankind. Hence her most glorious title of "Mother of God," which explains all her glories, her sanctity and her honour.
The Roman Missal, 1962
Luke 1. 26-35
And in the sixth month, the angel Gabriel was sent from God into a city of Galilee, called Nazareth, 27 To a virgin espoused to a man whose name was Joseph, of the house of David; and the virgin's name was Mary. 28 And the angel being come in, said unto her: Hail, full of grace, the Lord is with thee: blessed art thou among women. 29 Who having heard, was troubled at his saying, and thought with herself what manner of salutation this should be. 30 And the angel said to her: Fear not, Mary, for thou hast found grace with God.
31 Behold thou shalt conceive in thy womb, and shalt bring forth a son; and thou shalt call his name Jesus. 32 He shall be great, and shall be called the Son of the most High; and the Lord God shall give unto him the throne of David his father; and he shall reign in the house of Jacob for ever. 33 And of his kingdom there shall be no end. 34 And Mary said to the angel: How shall this be done, because I know not man? 35 And the angel answering, said to her: The Holy Ghost shall come upon thee, and the power of the most High shall overshadow thee. And therefore also the Holy which shall be born of thee shall be called the Son of God.
Please pray for us, O Holy Mother of God, that we made worthy of the promises of Christ. Amen