Jesus became what was true about us that we might become what is true about Him. “He made Him who knew no sin to be sin on our behalf, that we might become the righteousness of God in Christ.” 2 Corinthians 5:21.
The Christian life is not a reformed or improved life. The Christian life is a transformed life. We are called new creations in 2 Corinthians 5:17, and that particular Greek word used for “new” means “new, as in something that has never been seen before.” We should never be content with just being more righteous in our behavior than we used to be. The Holy Spirit, who leads us into all truth, says in 5:21 that we are “the righteousness of God in Christ.” How victorious is the righteousness of God in relationship to the reign of sin? Reining in life through the one Christ Jesus (Romans 5:17) is a daily life of crushing victory over the power of sin because our privilege is to abide in the righteousness or holiness of God that is ours in Christ whenever sin nips at our heels. The life of righteousness or holiness for the Christian is not a life of striving and struggling against the power of sin. If you try to attain a righteous life that way, then the law of sin will overcome every time. The glorious good news is that the very righteousness of God dwells in the person of Christ and because we are now in union with Jesus, God’s righteousness is our free gift. We don’t have to strive and struggle to be holy. We already are in Christ and the practical manifestation of that holiness is by faith in the righteousness of God that’s ours in Christ. You can’t attain what you already have. You can only manifest what’s yours already. Righteousness is not a thing; it is the person of Christ, and Christian victory is to moment by moment trust Him for holiness just like you at your new birth you trusted Him for your forgiveness.
Romans 1:17 NASB95
For in it the righteousness of God is revealed from faith to faith; as it is written, “BUT THE RIGHTEOUS man SHALL LIVE BY FAITH.”