While all of Advent is Marian, this Sunday focuses in a special way on the Blessed Mother and her unique graces, her key role in our salvation. Where would we be without Christ? And how could Christ have become man without the fiat of our Blessed Lady?
Moreover, as the Second Vatican Council teaches in the final chapter of Lumen Gentium, Mary is a type and model of the Church. What she received in the first moment of her life, in her mother’s womb, we receive over time, becoming free from sin, becoming saved.
It would be a good Sunday to sing something special in her honor, asking for her help on the way, our star of the sea.
And, given the focus in Year A on the Fourth Sunday of Advent to St Matthew's account of the Annunciation to St Joseph – the Matthean parallel to the Lucan pericope of the Annunciation to the BVM – don't forget St Joseph.