God does not indicate what the “source” of the light was (note our sun doesn’t make an appearance until Day 4). Throughout the rest of the Bible we see that the Lord is the everlasting light (Is.60:19); Jesus said “I am the light of the world” (Jn 8:12) and 1 John 1:5 says “God is light; in Him there is no darkness at all”. We generally do not think of these references as a physical manifestation of light—we spiritualize it (well maybe you don’t, but I usually do).
However, let us look at Jesus on the Mount of Transfiguration: Matt 17: 2 There he was transfigured before them. His face shone like the sun, and his clothes became as white as the light. 3 Just then there appeared before them Moses and Elijah, talking with Jesus. Jesus is the Light of the world, and in this instance we see the physical manifestation of the His indwelling Light. Do you think that the Light that God called forth on Day One could actually be His Manifest Light, His presence on the Earth? Again in 1 Tim. 6:16 we are told that the King of Kings and Lord of Lords (Jesus) lives in unapproachable light. The eternal city needs no sun or moon because the glory of God gives it light, and the Lamb is its lamp thereof. (Re. 21:23). God is a being of light, maybe that is why the sci-fi writers like to depict the higher “evolved” creatures as beings of light.
God’s first creative move was to bring Light. No other processes needed to build a working world could happen until light was available. Light gives heat to sustain life , is essential in photosynthesis for growth, and enables all creatures to function. The earth and all that is in the earth absorbs the light. Are we absorbing God's light when we are in His presence?
If you will allow me a “preach” a little here—I want to show you a parallel between the story of the creation of the world and the process God takes us through to become a new creature in Him. When we are in chaos and darkness (the same condition on the earth before God started the process of Creation) the first element God brings is Light. We cannot come to God except we are drawn to Him through Jesus (Jn 14:6), the source of Light. We can’t see our condition in the dark; He must bring Light into our lives to show us our lost condition. His light creates an atmosphere in which we can LIVE, GROW and FUNCTION for Him. He fills us with His Light
Our light is veiled by our flesh, just as the light in Jesus (except on the Mt. Transfiguration) was veiled while He was on the earth. Did you, like me, sing “this little light of mine” in Sunday School? We begin with such a little light, but it should grow and become more evident as the process of transformation occurs in our life. Jesus was transfigured before men, He expects us to become transformed before men. A little girl once described another believer as “Jesus with skin on”. We are to be the vessel of His Light to the world, so they might see their way to Him.
Mt 5:14-16: You are the light of the world. A city on a hill cannot be hidden. 15 Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. 16 In the same way, let your light shine before men, that they may see your good deeds and praise your Father in heaven”.