4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
Who can fulfil the righteousness of the law? No one can, except Christ, the Son of God who became the Son of man, that He might fulfil the righteousness of the law on our behalf. Everyone has sinned and offended the law of God, and has become unrighteous. “As it is written, There is none righteous, no, not one” (Romans 3:10). So, the law of God cannot make the sinner righteous. As Paul said in an earlier verse, “For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh” (Romans 8:3). Christ became our perfect Sacrifice, by living a perfectly righteous life in obedience to the law, to take our condemnation of sin in His flesh.
When the perfection of Christ is credited to us, or when we are justified by the imputation of His righteousness, it will be evidenced by our righteous walk. When His righteousness becomes ours, we walk according to His righteousness through the enabling of His Spirit. Before, we could not fulfil the commandments of the law. Now in Christ, having His righteousness imputed to us and His Spirit to guide and strengthen us, we cease to walk after the flesh and its lusts, and begin to walk after the Spirit. Day by day, as we live in Christ, a new kind of life begins to emerge which is obedient to His righteous law.
Now, what we could not do in obedience to God, Christ not only has done for us, but also enables us to do by His Spirit. Is not that a most wonderful thing? What God demands, He also supplies! Because we cannot fulfil on our own what He demands of us, He gives it to us. Notice that Paul did not say “we fulfil the righteousness of the law”, but that “the righteousness of the law might be fulfilled in us”, while pointing to the Holy Spirit who is in us to lead us.
Having come to Christ, we can now overcome our sins that once defeated us. Now with the Holy Spirit’s help, we can live the kind of life that God requires of us. We once could not attain it on our own strength, but now in Christ, by His Spirit’s power, we can fulfil His righteous will. Praise the LORD!