|The Nativity - Lucas Cranach the Elder|
Mankind needed a savior because he, and all creation along with him, was infected with the disease of sin. Since Adam and Eve's first sin, when they disobeyed God's command not to eat of the fruit of the tree of the knowledge of Good and Evil in the Garden of Eden, sin entered creation. All people born since then are born suffering from this disease of sin. We are all born without true fear or trust in God. We are all born with the inclination toward sin, to commit actual sinful acts, and away from God. There is nothing we can do to rescue ourselves from this dreadful condition, or reconcile ourselves to God. The disease is terminal. This is why the Lord himself had to save us. This salvation he effected by taking on human flesh, being born under the law, living a sinless life, going to the cross to suffer and die as punishment for mankind's sinfulness, and rising from the dead three days later as the conqueror of sin, death and Satan.
Jesus came to dwell among us and be the sacrifice to atone for the guilt of our sin on that first Christmas about which Luke writes. He came to us at a specific time, in a specific place. He is no fairy story, but the central focus of all of human history. He comes to us and remains with us in his holy word, preached and read, and in his holy sacraments, properly administered. What good news for fallen, sinful humanity. May it bring great joy to all who hear it. For unto us is born this day in the city of David a Savior, who is Christ the Lord.