As soon as She hears the tidings, Mary hastens to the hill country, not out of lack of faith in the prophecy or lack of trust in the message, nor for having doubted the example that was proffered, but guided by the happiness of seeing the promise fulfilled, drawn by the will to render a service, moved by the inner impulse of her joy.
Already filled with God, where would She hasten, if not to the heights? The grace of the Holy Spirit does not know sluggishness. The benefits of the arrival of Mary and of the Lord’s presence are immediately made manifest, for “when Elizabeth heard the greeting of Mary, the babe leapt in her womb, and Elizabeth was filled with the Holy Spirit (Lk 1:41).
The child rejoiced, the mother was filled with the Holy Spirit. The mother did not react before her son; rather, since the son was filled with the Holy Spirit, he communicated this to his mother. John rejoiced; the spirit of Mary also rejoiced. The exultation of John communicates itself to Elizabeth; as for Mary, however, we are not told that She received the Spirit then, but that her spirit rejoiced. He who is beyond all understanding acted in His mother in an incomprehensible way – Elizabeth receives the Holy Spirit after conceiving; Mary received beforehand. Therefore, Elizabeth says to Mary: “Blessed are You who believed” (cf. Lk 1:45).
Likewise blessed are you who have heard and believed, for every soul that possesses faith conceives and brings forth the Word of God and knows His works. May the soul of Mary be within each one of you, to magnify the Lord: in each one be the spirit of Mary to rejoice in God. Although according to nature there is only one Mother of Christ, according to faith, Christ is the fruit of all; for every soul receives the Word of God as long it guards chastity with perfect purity, without stain and free from sin.
St. Ambrose. “An Exposition of the Gospel of St. Luke”