“God saw that the light was good; and God separated the light from the darkness.” (Genesis 1:4, NASB)
First, we observe that God sees or observes the light He has created. He observes that the light is good. Much like a painting, the nature or character of the artist can be seen in the creation. God, by creating light, has left the imprint of His nature upon it – it is good. The rest of creation is still in need of work. It has not yet been declared good.
God then separates light and darkness. As with much of Scripture the “how?” question is not answered. It was most likely with His command (see verse 3). We do not know what creation would be like if God had not separated light from darkness. Due to this separation though, we gain many things. It begins the sense of seasons or times. This will prove to be very important as the rest of creation comes into being. Also, we have what becomes a great analogy throughout Scripture of good and evil (2 Corinthians 6:14).