Mysterium: event and mystery. A man is born, who is the Eternal Son of the Almighty Father, the Creator of heaven and earth: in this extraordinary event the mystery of God is revealed. In the Word who becomes man the miracle of the Incarnate God is made manifest. The mystery sheds light on the event of the birth: a baby is adored by the shepherds in the lowly stable, at Bethlehem. He is “the Savior of the world”, “Christ the Lord” (cf. Lk 2:11). Their eyes see a newborn child, wrapped in swaddling cloths and placed in a manger, and in that “sign”, thanks to the inner light of faith, they recognize the Messiah proclaimed by the Prophets.
This is Emmanuel, God-with-us, who comes to fill the earth with grace. He comes into the world in order to transform creation. He becomes a man among men, so that in him and through him every human being can be profoundly renewed. By his birth he draws us all into the sphere of the divine, granting to those who in faith open themselves to receiving his gift the possibility of sharing in his own divine life.
This is the meaning of the salvation which the shepherds hear proclaimed that night in Bethlehem: “To you is born a Saviour” (Lk2:11). The coming of Christ among us is the centre of history, which thereafter takes on a new dimension. In a way, it is God himself who writes history by entering into it. The event of the Incarnation thus broadens to embrace the whole of human history, from creation until the Second Coming. This is why in the Liturgy all creation sings, voicing its own joy: the floods clap their hands, all the trees of the wood sing for joy, and the many coastlands are glad (cf. Ps 98:8, 96:12; 97:1).
~Pope St. John Paul II, Midnight Mass homily, 1998
P.S. I see that tomorrow I am going to regret choosing to label this year's "12 days" w/ 2016. Happy New Year!