Catechism of the Catholic Church

494 At the announcement that she would give birth to "the Son of the Most High" without knowing man, by the power of the Holy Spirit, Mary responded with the obedience of faith, certain that "with God nothing will be impossible": "Behold, I am the handmaid of the Lord; let it be [done] to me according to your word." ¹³⁹ Thus, giving her consent to God's word, Mary becomes the mother of Jesus. Espousing the divine will for salvation wholeheartedly, without a single sin to restrain her, she gave herself entirely to the person and to the work of her Son; she did so in order to serve the mystery of redemption with him and dependent on him, by God's grace: ¹⁴⁰

As St. Irenaeus says, "Being obedient she became the cause of salvation for herself and for the whole human race." ¹⁴¹ Hence not a few of the early Fathers gladly assert. . .: "The knot of Eve's disobedience was untied by Mary's obedience: what the virgin Eve bound through her disbelief, Mary loosened by her faith." ¹⁴² Comparing her with Eve, they call Mary "the Mother of the living" and frequently claim: "Death through Eve, life through Mary." ¹⁴³