Is it too early to be preparing for Christmas? The Catechism of the Catholic Church, in its section on the Incarnation, points out that the world spent hundreds of years preparing for the first Christmas.
Its explanation of the Advent Season and Christmas follows.
522 The coming of God's Son to earth is an event of such immensity that God willed to prepare for it over centuries. He makes everything converge on Christ: all the rituals and sacrifices, figures and symbols of the “First Covenant.” He announces him through the mouths of the prophets who succeeded one another in Israel. Moreover, he awakens in the hearts of the pagans a dim expectation of this coming.
523 St. John the Baptist is the Lord's immediate precursor or forerunner, sent to prepare his way. “Prophet of the Most High,” John surpasses all the prophets, of whom he is the last. He inaugurates the Gospel, already from his mother's womb welcomes the coming of Christ, and rejoices in being “the friend of the bridegroom”, whom he points out as “the Lamb of God, who takes away the sin of the world”. Going before Jesus “in the spirit and power of Elijah,” John bears witness to Christ in his preaching, by his Baptism of conversion, and through his martyrdom.
524 When the Church celebrates the liturgy of Advent each year, she makes present this ancient expectancy of the Messiah, for by sharing in the long preparation for the Savior's first coming, the faithful renew their ardent desire for his second coming. By celebrating the precursor's birth and martyrdom, the Church unites herself to his desire: “He must increase, but I must decrease.”
The Christmas mystery
525 Jesus was born in a humble stable, into a poor family. Simple shepherds were the first witnesses to this event. In this poverty heaven's glory was made manifest. The Church never tires of singing the glory of this night: The Virgin today brings into the world the Eternal And the earth offers a cave to the Inaccessible.
The angels and shepherds praise him And the magi advance with the star, For you are born for us, Little Child, God eternal!
526 To become a child in relation to God is the condition for entering the kingdom. For this, we must humble ourselves and become little. Even more: to become “children of God,” we must be “born from above” or “born of God.” Only when Christ is formed in us will the mystery of Christmas be fulfilled in us. Christmas is the mystery of this “marvelous exchange”:
“O marvelous exchange! Man's Creator has become man, born of the Virgin. We have been made sharers in the divinity of Christ who humbled himself to share our humanity.”
The mysteries of Jesus' infancy
527 Jesus' circumcision, on the eighth day after his birth, is the sign of his incorporation into Abraham's descendants, into the people of the covenant. It is the sign of his submission to the Law and his deputation to Israel's worship, in which he will participate throughout his life. This sign prefigures that “circumcision of Christ” which is Baptism.
528 The Epiphany is the manifestation of Jesus as Messiah of Israel, Son of God and Savior of the world. The great feast of Epiphany celebrates the adoration of Jesus by the wise men (magi) from the East, together with his baptism in the Jordan and the wedding feast at Cana in Galilee. In the magi, representatives of the neighboring pagan religions, the Gospel sees the first-fruits of the nations, who welcome the good news of salvation through the Incarnation. The magi's coming to Jerusalem in order to pay homage to the king of the Jews shows that they seek in Israel, in the messianic light of the star of David, the one who will be king of the nations.
Their coming means that pagans can discover Jesus and worship him as Son of God and Savior of the world only by turning towards the Jews and receiving from them the messianic promise, as contained in the Old Testament. The Epiphany shows that “the full number of the nations” now takes its “place in the family of the patriarchs”, and acquires Israelitica dignitas (is made “worthy of the heritage of Israel”).
529 The presentation of Jesus in the temple shows him to be the first-born Son who belongs to the Lord. With Simeon and Anna, all Israel awaits its encounter with the Savior the name given to this event in the Byzantine tradition. Jesus is recognized as the long-expected Messiah, the “light to the nations” and the “glory of Israel,” but also “a sign that is spoken against.” The sword of sorrow predicted for Mary announces Christ's perfect and unique oblation on the cross that will impart the salvation God had “prepared in the presence of all peoples.”
530 The flight into Egypt and the massacre of the innocents make manifest the opposition of darkness to the light: “He came to his own home, and his own people received him not.” Christ's whole life was lived under the sign of persecution. His own share it with him. Jesus' departure from Egypt recalls the exodus and presents him as the definitive liberator of God's people.