How do we know Christ's righteousness is necessary for salvation?

Christ's righteousness is necessary because, as stated in Romans chapter 9, Israel sought righteousness through the law but could not attain it. Our own efforts, no matter how diligent, cannot satisfy the perfect righteousness required by God. The doctrine of imputed righteousness is central to Reformed theology; it asserts that believers are credited with Christ's righteousness when they put their faith in Him (2 Corinthians 5:21). Thus, it is not our works, but Christ's work alone that secures our salvation, demonstrating the complete sufficiency of His atoning sacrifice.