Throughout the Old Testament and even in the New Testament we read about people filling up with fear when they realize that they are in the presence of God.
Even St. Peter cried out to Jesus, Leave me Lord, I am a sinful man. It was not that they thought that God was mean. It was that God was so holy that they were sure that they could not exist in his presence. Often God would tell the prophets, that they had no reason to fear, he was choosing them for a particular mission. Still, there was and is this fact that when we all participate in all that is not God we exclude ourselves from ever being in his presence.
When the angel Gabriel came to Mary, he called out to her in those words we recite at the beginning of the Hail Mary. He called her Full of Grace, and he also said, Fear Not!, Mary had no reason to fear. There was nothing about her that was not God. There was no sin in her.
God in his goodness and love decided to show us how much He loves us by becoming one of us. To do this He took up His presence in a human being, Mary. To be so close to God's presence, Mary is conceived by God's plan to be a person who has totally with no participation in any form of evil whatsoever. Mary was chosen not just for what she would do but for whom she was. Mary was totally holy. There was nothing about her that in any way participated in that which was not God, that participated in sin. Mary’s complete freedom from sin is what we celebrate today, the Immaculate Conception of Mary.
Totally different from Eve, the first woman, or from all people for that matter, Mary is was always united to God and always obedient to God. She would do all he instructed her to do. Therefore, she is obedient and accepts the mission to be the mother of the Lord.
Today’s solemnity reminds us that God’s plan is more marvelous then we could ever imagine. To make his holiness physical by becoming one of us on Christmas day, he would first prepare someone who would always be open to his holiness. Moses was afraid to stand before God because he recognized his own sinfulness. But there was nothing about Mary, that would contradict the holiness of God. She is Full of Grace. We celebrate her holiness today as we celebrate her Immaculate Conception.
 Exodus 3:5
 Saturday 8th December, 2007, Solemnity of the Immaculate Conception. Genesis 3:9-15, 20. Sing to the Lord a new song, for he has done marvellous deeds-Ps 97(98):1-4. Ephesians 1:3-6, 11-12. Luke 1:26-38.
 Luke 5:8
 Id 1, 30.
 The Immaculate Conception, a solemnity, is the patronal feast of the United States. It is one of the few Holy days of obligation on the Church calendar. As this feast occurs early in Advent, it is a perfect time to consider Mary and her important role in the celebration of Christmas. In 1854, Pope Pius IX's solemn declaration, Ineffabilis Deus, clarified with finality the long-held belief of the Church that Mary was conceived free from original sin. In proclaiming the Immaculate Conception of Mary as a dogma of the Church, the pope expressed precisely and clearly that Mary was conceived free from the stain of original sin. This privilege of Mary derives from God's having chosen her as Mother of the Savior; thus she received the benefits of salvation in Christ from the very moment of her conception. (The picture above shows her mother, Anna, with the infant Mary within her womb.) This great gift to Mary, an ordinary human being just like us, was fitting because she was destined to be Mother of God. The purity and holiness of the Blessed Virgin Mary is a model for all Christians.