The image of light dispelling darkness is central to our understanding of the incarnation and its meaning [Isaiah 9:2]. When Jesus was presented at the temple shortly after His birth, the aged Simeon recognized this child as "A Light of revelation to the Gentiles, and the glory of Your people Israel."
The metaphor of light makes sense only against a background of darkness. In the Bible, darkness is a rich metaphor that points to a double reality. In one sense, darkness points to the simple fact of human ignorance. Those who are "in the dark" are those who lack knowledge. To the Jewish mind, this metaphor had particular application to the Gentile world - a world that had not received the grace of God through the revelation of the Torah, the prophets, and the written revelation of God. Even today, we know that untold millions still dwell in deep darkness, having never heard about the one true God or of Jesus Christ, His only Son.
In a second sense, darkness refers to evil and willful blindness. This points beyond the mere fact of simple ignorance. In this sense, darkness refers to the fact that many will reject the light. As John explained, "He was in the world, and the world was made through Him, and the world did not know Him. He came into His own, and those who were His own did not receive Him."
This is hard to believe - the Son of God took on human flesh and came to live among sinful humanity, but the vast majority did not recognize Him for who He is.
As a celebration of light, Christmas is the festival that points to the glory of God in the revelation of the Son in Bethelehem's humble manger. We rightly point to Christ's birth as the central event of human history--the dividing line between the age of darkness and the age of light. This is reason enough to celebrate Christmas, for our response to this gift of light must be a celebration, thanksgiving, and rejoicing....
The image of light is central, not only to Christmas, but to Christianity. Jesus said: "I am the Light of the world; he who follows Me will not walk in the darkness, but will have the Light of life." [John 8:12] This is the sum and substance of Christmas. The people who have walked in darkness have seen a great light. Those who have lived in a dark land have now experienced the shining of the Light of life.
Taken from "The People Who Walk in Darkness Will See a Great Light" (used by permission).