Saint Thomas Aquinas: God saved the world through Mary's humility

The Blessed Virgin possessed many qualities for which she is to be praised. She was full of grace, as testified by the angel. She was chosen as the mother of God, and although she became the mother of God, she gloried in her humility alone, saying : "Because He has looked upon His humble handmaid" (Luke 1:48).

The Lord was looking for a woman through whom the human race could be saved, and through whom the opposite could be healed by the opposite. The human race was lost through pride, since the beginning of all sin is pride. It would not have been fitting for the humble Son to dwell in a proud mother, who was to save mankind through his humility. 

Thus, God considers only humility. In a sermon on the Assumption of the Blessed Virgin Mary, Augustine writes of her humility: "O true humility of Mary, who begot God for mankind, made life known to mortals, opened the heavens, purified the world, revealed Paradise to man, and freed the souls of men!

<Saint Thomas Aquinas, Sermon