What is human righteousness compared to?
Human righteousness is compared to filthy rags. Scripture sets it in contrast to the righteousness of God, which is apart from the law. The law cannot justify anyone; it only gives the knowledge of sin and condemns. Therefore, no flesh is justified by keeping the law.
Les explains that Paul wrote in verse 20 that by the deeds or keeping of the law shall no flesh be justified, for by the law is the knowledge or awareness of sin. That law could do nothing but condemn; it had no power even to help the Jew be a law keeper. Then verse 21 introduces the contrast with the little word “but.” Les teaches that the righteousness of God is not human righteousness, for human righteousness is like filthy rags. Instead, the righteousness of God is without the law. This also connects to the precepts that without faith you cannot please God and without the shedding of blood there is no remission, which goes back to the cross.