The first separation was between light and darkness. This was the fourth requirement for generating life. This separation was for the purpose of discerning day from night, causing the light to be set apart. This is more difficult to understand, but an illustration will make it clear.
Immediately after you were saved, you didn't have any discernment and were unable to distinguish between light and darkness. After you were saved awhile and had gone on with the Lord, gradually there was a separation within you and you had the discernment to say, "This is light and that is darkness. I will keep the light, but not the darkness." Before we were saved, we had no day at all, only a night of twenty-four hours. We were constantly in the night, a dark and cloudy night with no stars. But, praise the Lord! From the day we were saved, something began to dawn like the morning. This is the day.
Perhaps your first day was only four hours long, and then evening came again. Regardless of how long it was, you had your first day. Praise the Lord! After ten hours of night, you came to a meeting and in that meeting you saw the dawn. It was another day and you shouted, "Hallelujah!" Then you went to school or to work and evening came again. Don't be disappointed—evening is a sign that morning will come. Also, when you are in the morning, be prepared for the evening to come again. In Genesis 1:5, it doesn't say morning and evening; it says evening and morning because we came out of the night. "And evening and morning were the first day." Praise the Lord!
With the young people the night is always longer, but with the old folks the night is shorter. Because I am experienced, my spiritual day is longer than yours. My spiritual day is nineteen hours and my spiritual night only five hours. When we get into the New Jerusalem, there will be no night at all (Rev. 21:25). You need to grow. Perhaps your day is just ten hours and your night fourteen hours. You need to grow for your days to be longer and your nights to be shorter.
We need the separation of day and night, the discernment between light and darkness. In 2 Corinthians 6:14, Paul asks, "What fellowship has light with darkness?" This word must also refer to Genesis 1. God has separated light from darkness; so don't try to mix them. Light has nothing to do with darkness. What kind of fellowship can light have with darkness? This means that we are children of light and that we shouldn't be yoked or mingled with the people living in darkness. We must maintain the separation. They are children of darkness and we are children of light. We all must say, "What communion can there be between light and darkness?" This is a real separation. If we keep this requirement, we will have more light.