"Jesus Christ, the son of David, the son of Abraham." This is the first sentence of the gospel read at the Sunday before the Nativity in the Orthodox Church. I suggest the gospel reading actually should begin with the first "real" ancestor of our Lord God and Savior Jesus Christ.
Of course, the reason the gospel starts with Abraham is because, despite being surrounded by polytheistic, idol worshipping, pagans, Abraham acknowledged that God is unseen and one. God made a covenant with him that made him the leader of God's people — the people of the First Covenant (Genesis 17) — and the "father of many nations."
A complete understanding the nativity of Our Lord reaches back even farther, to the first ancestor of mankind: Adam. In Hebrew "Adam" means "man." Adam too, is a first ancestor of Our Lord, in that Jesus was both fully human (being born of woman) just like all mankind, although fully God as well by being conceived of the Holy Spirit.
The scripture account is a narrative but also a great theological mystery. Adam and Eve were made in God's image and called to be like Him. They start out in Paradise with the potential of full union with God but still experienced testing. They fail the test by the sin of pride. They are cast out of paradise into the world and are disordered — inclined to sin and destined for death. We are the offspring of Adam and partake of these same maladies.
Everything in the Orthodox Church tradition — the Scripture, the Church Fathers, the Divine Liturgy and other worship services, the architecture of the temple [building] the icons and the iconostas, and more — tell the story of salvation from the primordial beginnings.
For example, every Church has an iconostas, a screen of icons with three doors, a middle or royal door before the altar, a north door to the left, and a south door to the right separating the holy of holies or altar area from main area where the people of God are located. This symbolizes the separation between mankind and the kingdom and the paradise that was lost after Adam's sin. The icons function as windows to heaven (or paradise).
The relation between paradise and the heavenly kingdom is a great mystery. St. Gregory of Sinai talks about a "paradise of Eden and a paradise of grace." Nikitas Stithatos, the disciple and biographer of St. Symeon the New Theologian tells us, "...we should learn what the kingdom of heaven is, what the kingdom of God is, and what paradise is, and how the one differs from the other;" (Philokalia, V 4). Or consider the words of Our Lord to the thief on the cross, "today you will be with me in paradise" (Luke 23:43).
In the Divine Liturgy paradise is at least paralleled with the Kingdom of God. The priest starts the Liturgy in front of the altar (which seen though the open Royal Doors) by chanting, "Blessed is the Kingdom of the Father, and of the Son, and of the Holy Spirit."
The icon of St. Michael the Archangel who expelled Adam and Eve from paradise is on the north door of the iconostasis. St. Michael to this day prevents all, except those who have earned it, from getting into the Kingdom. The archangel at the south door is Gabriel who said to Mary, "Hail (Ave) Full of Grace ...you are to bear the Son of God...." She responded, "Be it done unto me according to your word." Gabriel's gift to mankind is to announce the the way back to the Kingdom, to paradise (Luke 1: 28-38). Mary's response to God's invitation, her consent to the command of God through Gabriel becomes the a key that opens the door of paradise to all mankind.
Our Lord voluntarily "emptied" (kenosis) Himself when He took on human nature through Mary. In the Divine Liturgy of the Orthodox Church this self-emptying is twice proclaimed. During the Small Entrance, the priest exits the sanctuary through the north door carrying the book of the Gospels — the Word of God. He who was born in the flesh comes out of paradise to be among us who are presently out of the Kingdom to give us His Word. This liturgical action is a beautiful symbol of the public life of Jesus when He taught His disciples and apostles and still teaches us today. After few hymns, the priest returns to the sanctuary through the Royal Doors, a liturgical action representing a return to the Kingdom of God.
The second exit a little later is at the Great Entrance. Ordinary bread and wine is carried in procession by the priest again out of the same North door and brought back through the Royal Door and laid on the altar. The bread and wine will be transformed into the very body and blood of Our Lord and Savior Jesus Christ, when the priest says the words of Jesus, "This bread is my body, this wine is my blood" and asking that it be blessed by the Holy Spirit.
Holy Communion was instituted at the Last Supper and the events that followed it: the passion, death and resurrection of Christ conquered death and opened the door for those 'in whom He now indwells' to enter the Kingdom. The Nativity started this salvific act. Mary, the teenage virgin from Palestine, by her simple obedience was the key that allowed Emmanuel (God with us) to bring us salvation. She became the "New Eve," the Theotokos (God-bearer), Our Mother. The Nativity is united with the whole life of Jesus, his teaching, the Last Supper, Calvary, and the Resurrection.
The Nativity is understood in our heart, not in rush and press of a commercialized Christmas. The secularists who want to remove the word Christmas from the public square by taking Christ out of Christmas and replace it with an X, who want to ban Christmas trees or Nativity scenes, who won't allow children to sing a carol in school, may unwittingly have point. The real meaning of Christmas is to have Christ born in us, indwelling in our hearts.