18 This blessing reaches its full meaning when Mary stands beneath the Cross of her Son (cf. Jn. 19:25). The Council says that this happened "not without a divine plan": by "suffering deeply with her only-begotten Son and joining herself with her maternal spirit to his sacrifice, lovingly consenting to the immolation of the victim to whom she had given birth," in this way Mary "faithfully preserved her union with her Son even to the Cross." It is a union through faith- the same faith with which she had received the angel's revelation at the Annunciation. At that moment she had also heard the words: "He will be great...and the Lord God will give to him the throne of his father David, and he will reign over the house of Jacob for ever; and of his kingdom there will be no end" (Lk. 1:32-33). And now, standing at the foot of the Cross, Mary is the witness, humanly speaking, of the complete negation of these words. On that wood of the Cross her Son hangs in agony as one condemned. "He was despised and rejected by men; a man of sorrows...he was despised, and we esteemed him not": as one destroyed (cf. Is. 53:3- 5). How great, how heroic then is the obedience of faith shown by Mary in the face of God's "unsearchable judgments"! How completely she "abandons herself to God" without reserve, offering the full assent of the intellect and the will" to him whose "ways are inscrutable" (cf. Rom. 11:33)! And how powerful too is the action of grace in her soul, how all-pervading is the influence of the Holy Spirit and of his light and power! Through this faith Mary is perfectly united with Christ in his self- emptying. For "Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men": precisely on Golgotha "humbled himself and became obedient unto death, even death on a cross" (cf. Phil. 2:5-8). At the foot of the Cross Mary shares through faith in the shocking mystery of this self- emptying. This is perhaps the deepest "kenosis" of faith in human history. Through faith the Mother shares in the death of her Son, in his redeeming death; but in contrast with the faith of the disciples who fled, hers was far more enlightened. On Golgotha, Jesus through the Cross definitively confirmed that he was the "sign of contradiction" foretold by Simeon. At the same time, there were also fulfilled on Golgotha the words which Simeon had addressed to Mary: "and a sword will pierce through your own soul also."
Source: Redemptoris Mater (Vatican.va)