39 From this point of view we must consider once more the fundamental event in the economy of salvation, namely the Incarnation of the Word at the moment of the Annunciation. It is significant that Mary, recognizing in the words of the divine messenger the will of the Most High and submitting to his power, says: "Behold, I am the handmaid of the Lord; let it be to me according to your word" (Lk. 1:38). The first moment of submission to the one mediation "between God and men"-the mediation of Jesus Christ-is the Virgin of Nazareth's acceptance of motherhood. Mary consents to God's choice, in order to become through the power of the Holy Spirit the Mother of the Son of God. It can be said that a consent to motherhood is above all a result of her total selfgiving to God in virginity. Mary accepted her election as Mother of the Son of God, guided by spousal love, the love which totally "consecrates" a human being to God. By virtue of this love, Mary wished to be always and in all things "given to God," living in virginity. The words "Behold, I am the handmaid of the Lord" express the fact that from the outset she accepted and understood her own motherhood as a total gift of self, a gift of her person to the service of the saving plans of the Most High. And to the very end she lived her entire maternal sharing in the life of Jesus Christ, her Son, in a way that matched her vocation to virginity. Mary's motherhood, completely pervaded by her spousal attitude as the "handmaid of the Lord," constitutes the first and fundamental dimension of that mediation which the Church confesses and proclaims in her regard and continually "commends to the hearts of the faithful," since the Church has great trust in her. For it must be recognized that before anyone else it was God himself, the Eternal Father, who entrusted himself to the Virgin of Nazareth, giving her his own Son in the mystery of the Incarnation. Her election to the supreme office and dignity of Mother of the Son of God refers, on the ontological level, to the very reality of the union of the two natures in the person of the Word (hypostatic union). This basic fact of being the Mother of the Son of God is from the very beginning a complete openness to the person of Christ, to his whole work, to his whole mission. The words "Behold, I am the handmaid of the Lord" testify to Mary's openness of spirit: she perfectly unites in herself the love proper to virginity and the love characteristic of motherhood, which are joined and, as it were, fused together. For this reason Mary became not only the "nursing mother" of the Son of Man but also the "associate of unique nobility" of the Messiah and Redeemer. As I have already said, she advanced in her pilgrimage of faith, and in this pilgrimage to the foot of the Cross there was simultaneously accomplished her maternal cooperation with the Savior's whole mission through her actions and sufferings. Along the path of this collaboration with the work of her Son, the Redeemer, Mary's motherhood itself underwent a singular transformation, becoming ever more imbued with "burning charity" towards all those to whom Christ's mission was directed. Through this "burning charity," which sought to achieve, in union with Christ, the restoration of "supernatural life to souls," Mary entered, in a way all her own, into the one mediation "between God and men" which is the mediation of the man Christ Jesus. If she was the first to experience within herself the supernatural consequences of this one mediation-in the Annunciation she had been greeted as "full of grace"-then we must say that through this fullness of grace and supernatural life she was especially predisposed to cooperation with Christ, the one Mediator of human salvation. And such cooperation is precisely this mediation subordinated to the mediation of Christ. In Mary's case we have a special and exceptional mediation, based upon her "fullness of grace," which was expressed in the complete willingness of the "handmaid of the Lord." In response to this interior willingness of his Mother, Jesus Christ prepared her ever more completely to become for all people their "mother in the order of grace." This is indicated, at least indirectly, by certain details noted by the Synoptics (cf. Lk. 11:28; 8:20-21; Mk. 3:32-35; Mt. 12:47-50) and still more so by the Gospel of John (cf. 2:1-12; 19:25-27), which I have already mentioned. Particularly eloquent in this regard are the words spoken by Jesus on the Cross to Mary and John.
Source: Redemptoris Mater (Vatican.va)