The Lord Magnified in us

Universalis: Office of Readings:

"Blessed are you,” said Elizabeth, “who believed”.
You too, my people, are blessed, you who have heard and who believe. Every soul that believes — that soul both conceives and gives birth to the Word of God and recognises his works.

Let the soul of Mary be in each one of you, to proclaim the greatness of the Lord. Let the spirit of Mary be in each one of you, to rejoice in God. According to the flesh only one woman can be the mother of Christ but in the world of faith Christ is the fruit of all of us. For every soul can receive the Word of God if only it is pure and preserves itself in chastity and modesty.

The soul that has been able to reach this state proclaims the greatness of the Lord just as Mary did and rejoices in God its saviour just like her.
The Lord’s greatness is proclaimed, as you have read elsewhere, where it says Join me in magnifying the Lord. This does not mean that anything can be added to the Lord’s greatness by human words, but that he is magnified in us. Christ is the image of God and so any good or religious act that a soul performs magnifies that image of God in that soul, the God in whose likeness the soul itself was made. And thus the soul itself has some share in his greatness and is ennobled."

---from St Ambrose's commentary on St Luke's Gospel