Every word spoken in the Bible has a carefully embedded principle that God wants to teach. The smallest narratives and littlest details can have the most profound of teachings, and this is what we find in the account of the second day of creation -- the only day of creation that God did not declare to be good.
The second day was the day that God made the heaven and waters. The way that God did so was by separating them both by forming a horizon. He took all the water particles He had formed and brought them together to form the seas and oceans. God then took all the air particles and made the atmosphere.
In Genesis 1:8, it says, "And God called the expanse Heaven. And there was evening and there was morning, the second day." Looking at all the other five days of creation, God would end one working day by calling all He had made good. And there is the second day when God looked at what He had done and just said, "Alright, that's it for today."
It isn't until verse 10, where God starts gathering up the waters of the earth, that God declares that the waters and land are good: "God called the dry land Earth, and the waters that were gathered together he called Seas. And God saw that it was good."
There is a principle behind this deliberately and intentionally thought out word. God couldn't have just forgotten to say that the second day was good too. So what was God trying to teach?
Division is never good
The second day was the only day of division in creation. Every other day was meant to unite or give life except the second day. It was only until He gathered the waters in one place that He called them good because God is not a God of division but of unity.
The principle that God teaches here is that our God has never been a fan of separation and division. Although division is often necessary, God never declares the work complete until there is redemption.
God is the biggest fan of unity
God exists all for oneness and unity. His very being exists as a perfect tri-unity. In the same way, God wants us men to exist in community as well, desiring only that we come together and value relationship more than factions and subsections.
That is why God believes in a universal church, brought together by the universal truth. God is not a God of eternal separation, but One that would allow separation only because there is the day of reconciliation to look forward to.
Ephesians 2:13-16 declares that Jesus came to "...reconcile us both to God in one body through the cross, thereby killing the hostility."
