The origin of light is explained by God's purpose and nature, whom the apostle John described as not only the Creator of light, but in a broad sense as light itself: God is light.
Please turn to I John 1, verse 5. God is light just as much as He is love and truth and spirit. Spirit and light are expressions of His essential nature and love is the expression of His personality corresponding to His nature. God not only loves but is love. It is His very nature, and He imparts this nature to the realm in which His children dwell in light.
The darkness mentioned in verses 5 and 6 is the universal symbol and condition of sin and death. In direct contrast, light mentioned in verse 7 is the symbol and expression of holiness. God, by His presence and grace, is to His holy priesthood and His holy nation as a marvelous light.
This biblical vision, which closes with the breathtaking hope of the New Jerusalem, where God Himself will be our everlasting light and where night will be no more, testifies to the eternal promise of God's presence. Until then we are called to walk in the light as He is in the light, reflecting the radiance of Christ so that others may also see the way of eternal life in the Kingdom of God.