The angel Gabriel was sent from God to a town of Galilee called Nazareth, to a virgin betrothed to a man named Joseph, of the house of David, and the virgin’s name was Mary. And coming to her, he said, “Hail, full of grace! The Lord is with you.” Luke 1:26–28
What does it mean to be “full of grace?” This is a question at the heart of our solemn celebration today.
Today we honor the Blessed Virgin Mary, the Mother of the Savior of the World, under the unique title of “The Immaculate Conception.” This title acknowledges that grace filled her soul from the moment of her conception, thus preserving her from the stain of sin. Though this truth had been held for centuries among the Catholic faithful, it was solemnly declared as a dogma of our faith on December 8, 1854, by Pope Pius IX.
By raising this doctrine of our faith to the level of a dogma, the holy father declared that this truth is to be held as certain by all the faithful. It is a truth that is found in the words of the angel Gabriel, “Hail, full of grace!” To be “full” of grace means just that. Full! 100%. Interestingly, the Holy Father did not say that Mary was born in a state of Original Innocence as were Adam and Eve before they fell into Original Sin. Instead, the Blessed Virgin Mary is declared to be preserved from sin by “a singular grace.”
Though she had not yet conceived her Son, the grace that He would win for humanity by His Cross and Resurrection was declared to have transcended time so as to heal our Blessed Mother at the moment of her conception, preserving her of even the stain of Original Sin, by the gift of grace.
Why would God do this? Because no stain of sin could be mingled with the Second Person of the Most Holy Trinity. And if the Blessed Virgin Mary were to become a fitting instrument by which God unites with our human nature, then she needed to be preserved from all sin. Additionally, she remained in grace throughout her life, refusing to ever turn from God by her own free will.
https://catholic-daily-reflections.com/2023/12/07/full-of-gods-grace-3/