"For God, who said, “Light shall shine out of darkness,” is the One who has shone in our hearts to give the Light of the knowledge of the glory of God in the face of Christ."
2 Corinthians 4:6
Paul gives us a beautiful picture of spiritual conversion in this verse. The God who brought physical light out of darkness, is able to illumine our darkened hearts with knowledge of Himself. So that we who once walked in ignorance of God's glory, now understand it in the person of Christ. This is the fulfillment of Isaiah's prophecy of the Messiah:
"The people who walk in darkness
Will see a great light;
Those who live in a dark land,
The light will shine on them."