The Most Blessed Trinity revealed the first part of it to us and the latter part was added by Saint Elizabeth who was inspired by the Holy Spirit. Holy Mother Church gave us the conclusion in the year 430 when she condemned the Nestorian heresy at the council of Ephesus and defined that the Blessed Virgin is truly the Mother of God. At this time she ordered us to pray to Our Lady under this glorious title by saying:
"Holy Mary, Mother of God, pray for us sinners, now, and at the hour of our death."
The greatest event in the whole history of the world was the Incarnation of the Eternal Word by Whom the world was redeemed and peace was restored between God and men. Our Lady was chosen as His instrument for this tremendous event and it was put into effect when she was greeted with the Angelic Salutation. The Archangel Gabriel, one of the leading princes of the heavenly court, was chosen as ambassador to bear these glad tidings.
In the Angelic Salutation can be seen the faith and hope of the patriarchs, the prophets and the Apostles. Furthermore it gives to Martyrs their unswerving constancy and strength, it is the wisdom of the doctors of the Church, the perseverance of holy confessors and the life of all religious. (Blessed Alan de la Roche) It is also the new hymn of the law of grace, the joy of Angels and men, and the hymn which terrifies devils and puts them to shame.
By the Angelic Salutation God became man, a virgin became the Mother of God, the souls of the just were delivered from Limbo, the empty thrones in Heaven filled. In addition sin was forgiven, grace was given to us, sick people were made well, the dead were brought back to life, exiles were brought home, and the anger of the Most Blessed Trinity was appeased and men obtained eternal life.
Finally, the Angelic Salutation is a rainbow in the heavens, a sign of the mercy and grace which God has given to the world. (Blessed Alan da la Roche)
From page 42 and 43
Nihil Obstat, Gulielmus F. Hughes, S.T.L., Censor Librorium
Imprimatur, Thomas Edmundus Molloy, S.T.D., Archiepiscopus-Episcopus Brooklyniensis, 1954 For more, see The Holy Rosary
St. Louis-Marie Grignon de Montfort's The Secret of the Rosary