"Rejoice, you who are full of grace"
In Mary, the Holy Spirit manifests the Son of the Father, now become the Son of the Virgin. She is the burning bush of the definitive theophany. Filled with the Holy Spirit she makes the Word visible in the humility of his flesh. It is to the poor and the first representatives of the gentiles that she makes him known.
Source: Catechism of the Catholic Church (Vatican.va)