"O admirabile commercium: O marvellous exchange! Man’s Creator has become man, born of a Virgin. We have been made sharers in the divinity of Christ who humbled himself to share in our humanity.” Thus the antiphon for First Vespers of January 1 expresses the mystery of the Incarnation. And the “Mass” part of the Christ-Mass season perpetuates this mystery and continues to invite us to live it as the finality of our daily existence. For at the offertory of every Mass, as he mingles a drop of water with the wine in the chalice, the priest prays quietly on our behalf that “By the mystery of this water and wine, we may  come to share in the divinity of Christ, who humbled himself to share in our humanity.”