Why is the concept of God being self-existent important for Christians?

The concept of God's self-existence is vital to Christian theology as it emphasizes that God is the ultimate source of existence and does not rely on creation or anything external to define who He is. As stated in Hebrews 11:6, we must believe that He is. This self-existence speaks to His eternal nature and sovereignty; God is unchanging and perfect in Himself. He does not gain or lose anything based on His creation, which ensures that His promises and character remain constant and trustworthy, providing comfort and assurance to believers.