The Magnificat antiphon for Second Vespers sings: "This day a shoot from the stock of Jesse has budded forth. This day, Mary was conceived without stain of sin. This day, she crushed the ancient serpent's head, alleluia!" The Gregorian chant for this antiphon echos and mirrors the antiphon for Christmas day, 'Hodie Christus natus est', clearly underlining the link between that great Feast of our salvation and today's Feast of the Immaculate Conception of Mary. Hence, St John Damascene can add: "Today the ears of the whole world are listening to news of joy. The heavens above rejoice, the earth beneath exults... He will tear to pieces the garments of our old mortality."
Today's joy overflows into the Third Sunday of Advent, Gaudete Sunday, which keynote is rejoicing and the exultation of Israel in her redemption. Indeed, our Lady is present in this Sunday's liturgy both in the responsorial canticle, which is her song of exultation, the Magnificat, and in Isaiah's proclamation of joy, which echoes today's Second antiphon at First Vespers: "I rejoice heartily in the Lord... for he has clothed me with a robe of salvation."