Genesis 1:6-8 meaning

God said, "Let there be an expanse" (v 6). The expanse is simply space, space that separates the waters from the waters (v 6). This means the waters of the heavens from the waters of the earth. The word waters may mean water gathered in a liquid state or moisture, seeming to imply that the earth was encased in dense moisture (or water). When God separated the waters, He called this space heaven, which is the sky. This was the second day of creation.

The Bible uses the themes of water and fire from beginning to end. 2 Peter 3:5-6 says, "For when they maintain this, it escapes their notice that by the word of God the heavens existed long ago and the earth was formed out of water and by water, through which the world at that time was destroyed, being flooded with water." God both formed the earth out of water as well as destroying that same earth by water during Noah's time (Genesis 7).

God promised He would not destroy the earth with water again. 2 Peter 3:7 says "But by His word the present heavens and earth are being reserved for fire, kept for the day of judgment and destruction of ungodly men." We look forward to the New Earth in hope, which will no longer have any sea (Revelation 21:1).

The Hebrew word for Heaven is Hashamayim. Many in the Jewish tradition hold that Hashamayim is a combination of the words Aish which means "fire," and Mayim which means "water." They conclude that this construction is due to the physical nature of the universe—that it is a balance of judgment and mercy.