How do we know we can't earn our salvation?

Salvation is fundamentally a gift of grace. Ephesians 2:8-9 reminds us that we are saved by grace through faith, and this is not of ourselves, it is the gift of God, not of works, lest any man should boast. The evidence of depravity is seen in our inclination to think we have some contribution to our salvation. The Bible emphasizes that all have sinned and fall short of the glory of God (Romans 3:23), indicating that human efforts cannot bridge the gap created by sin. Instead, we rely on the completed work of Jesus Christ, who paid the debt for our sins on the cross (John 3:16). Our salvation, thus, is entirely from Him, ensuring that He alone receives the glory.