Genesis 1:3-5

3 And God said, “Let there be light,” and there was light. 4 And God saw that the light was good. And God separated the light from the darkness. 5 God called the light Day, and the darkness he called Night. And there was evening and there was morning, the first day

Its important to note that the first time I read this I made a huge mistake into thinking that the creation of light meant the creation of the sun, moon and stars.  I read 'let there be lights', not 'light', and so my initial notes for this verse actually apply more to verses 14-20.  It was a rookie mistake, I've never read over creation enough times to remember what was created on each day.   The notes that follow are the notes made after realising my error. 

The light that God creates on the first day of creation reflects the initial enlightenment of our souls when we come to know Christ.  I know that the first day I gave my heart and life to Christ, when I heard God speak so clearly to me,  I felt truly enlightened.  It was as if God had been waiting above the dark of my empty soul and suddenly whispered 'let there be light'.  He created light inside of me the same way he created light in the empty world.  

It is no surprise that God created light first.  We are told continuously throughout the Bible that God is light(1 John 1:5), that he brings us into the light (Ephesians 5:8) and that he continues to guide our path with his light (Psalm 119:105).  We also know that there is no darkness within God, for he is holy and pure, and so maybe this is why he separates the dark and light.   Perhaps he gave day and night in order to show the relation between the Spirit and flesh.  When one is advancing the other is receding, and they're never still or stagnant (Galatians 5:17).

Without Christ, the light that we now get to encounter would be withdrawn and distant.  God is light and we were darkness, and those two do not co-exist.  It is only through Christ, and what he endured on the cross, that the promise of Isaiah 60:20 is fulfilled 

Your sun shall no more go down, nor your moon withdraw itself; for the Lord will be your everlasting light, and your days of mourning shall be ended.

For I know that it is now the Lord who is my light. My life nor days are ruled by sin or worldly forces of darkness.  I am now living in the light, and it is my constant prayer to walk in the light of God.  But I also know that when I am called home, or upon Jesus' return to Earth, we will fully see that light.

And the city has no need of sun or moon to shine on it, for the glory of God gives it light, and its lamp is the Lamb.

Revelation 21:23

I'm not sure if the light that was created in the beginning was the light of the glory of God, and what we experience in this world now is limited by the fall.  Or whether the light he created on that first day was just an echo, a reflection, a small piece of the jigsaw puzzle to help us better understand the bigger picture. But I do know that God is light, and full of light, and He extends that light to me and you, having forgiven our sins through Christ's crucifixion.