How do we know that grace is necessary for salvation?

As highlighted in Ephesians 2:8-9, salvation is by grace through faith, not of works, so that no one can boast. Paul's experience, as outlined in Galatians 5, underscores that relying on the law or personal merit nullifies grace. To be justified by the law is to fall from grace because grace alone grants the ability to believe in Christ. The transformative power of grace changes our perspective, leading us to understand that our righteousness is found solely in Christ. Without this grace, one's efforts are in vain, as true justification before God rests completely on His unmerited favor.