@hebrew.
To we humans without light we can't do anything. God has already established the light in heaven, so the heavens were filled with light. God so cared for us that He don't want to leave us in darkness, then He said: "let this light in the sky shine down on the earth, and it was so".

This light became the day that we enjoy today. God understood that we are all children of light hence He established the light in other for us His children to shine in the light of His glory.

God made two greats lights, the greater light to rule the day and the lesser light to rule the night. These are two great lights that God established, but one is greater than one. The one that is greater is called day. In the day time the sun gives light and heat.

The lesser one is the moon. Without the moon at night everywhere would have been dark. The sun comes with full voltage and at evening hour, it withdrew back. Then the moon emerges to give us the evening light
The light of the moon is not as bright as the sun. But if not for the light of the moon, we would not have been able to see in the night hour.

Genesis 1

The earth was without formed and darkness covered the face of the deep.

It is the sun that brought about day while the moon brought night.

Wonderful post @hebrew. God continue to bless you for your support on my blog.

Shalom