What is the firmament the Bible talks about?

from the old testament

• The King James Version of the Bible refers to the firmament seventeen times. The word is a translation of the Latin word firmamentum, meaning something that strengthens or supports. In biblical references, it refers to an expanse, and generally to the sky or to heavens.
• The first occurrences of this word are found in Genesis 1:6–8 (KJV) that reads, "And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. And God called the firmament Heaven. And the evening and the morning were the second day." These verses call the firmament "heaven;" the original Hebrew word there means "sky" or "heaven."
• Modern translations render the word the KJV translates "firmament" as "expanse," "vault," "space," or "dome." They render God's naming of that space as "sky" or "heaven." In short, it seems to be a references to the visible area above the earth.
• Genesis 1:2–5 indicates God created light on the first day and that water already existed on or by day one. Day two adds the creation of sky to divide the waters. Some also believe there continued to be "water above the sky" that in some way contributed to the long age spans of people living before the flood in Noah's time. However, this is not necessary as the passage describes the dividing of a watery world rather than sky between two bodies of water. This division of the water continued on the third day as the water, now separated from the sky, was then gathered into bodies of water called "seas." This reference to "seas" was likely concerning all large bodies of water.
• In Genesis 1:16–17, God placed the sun, moon, and stars in this "firmament." Similar to other ancient writings, Genesis 1 groups stars, sun, moon, and planets together at times, referring to the "heavenly beings" that are seen in the sky. Sky from the Jewish perspective could refer to everything a person could see above the land.
• Interestingly, this power to divide or control the waters is later seen in interesting ways. God floods the Earth with water in the flood of Noah's time (Genesis 6—9). Later, He divides the Red Sea to allow Moses and the Israelites an opportunity to escape Egypt (Exodus 14). God divided the Jordan River when Joshua and the Israelites entered into the Promised Land (Joshua 3). Elijah, and Elisha would each divide the waters of the Jordan River by God's power (2 Kings 2). Jesus would later calm the stormy waters (Mark 4:35–41) and even walk on water to demonstrate His divine power (Matthew 14:22–33).
• The word "firmament" is seen again in the Book of Psalms. Psalm 19:1 (KJV) states, "The heavens declare the glory of God; and the firmament sheweth his handywork." Psalm 150:1 (KJV) says, "Praise ye the LORD. Praise God in his sanctuary: praise him in the firmament of his power."
• Both the prophets Ezekiel and Daniel use this word. Ezekiel references an expanse above the heads of angelic beings in his visions (Ezekiel 1:24–26; 10:1). Daniel refers to wise people shining "like the brightness of the sky above" (Daniel 12:3, ESV).

from the new testament

• The word "firmament" is not used in the New Testament.

implications for today

The firmament illustrates God's order and sovereignty over His creation and reminds us of the importance of recognizing God's authority and the beauty of His creation. Just as the firmament serves as a boundary and a display of God’s handiwork, our lives are also filled with boundaries set by God for our protection and flourishing. His commands provide moral clarity and guidance for righteous living (Psalm 119:105). He also exposes our sinfulness and warns us of following our own desires and pursuits, encouraging us instead to seek first His kingdom and righteousness (Matthew 6:33). Additionally, God places boundaries in relationships, urging us to love one another as He has loved us (John 13:34–35) and to avoid harmful influences that can hinder our spiritual growth (1 Corinthians 15:33). These boundaries are not restrictive but liberating, leading us toward a life of purpose and fulfillment in His divine order. By contemplating the firmament, we are reminded of God's continuous involvement in His creation and His unwavering presence in our own lives, encouraging us to live in a way that reflects His divine order and sovereignty.