God is associated with light throughout Scripture. His light began the creation of the world. The light of a star led the wise men to Jesus. The light of angels announced His birth as well as His resurrection. Jesus called Himself the Light of the world, and this Light has been given to us.
Isaiah wrote these words during bleak times for Israel. They had endured much suffering and captivity. In the preceding chapter of Isaiah, he says that people saw only distress and darkness and fearful gloom. That may be an accurate description of how we see our personal lives as well as the world in general. But God’s answer to that is the light of Christ’s birth, death, and resurrection.