Sometimes people are careless and speak disparagingly of all human righteousness, as if there were no such thing that pleased God. They often cite Isaiah 64:6 which says our righteousness is as filthy rags. It is true – gloriously true – that none of God’s people, before or after the cross, would be accepted by an immaculately holy God if the perfect righteousness of Christ were not imputed to us (Romans 5:19; 1 Corinthians 1:30; 2 Corinthians 5:21). But that does not mean that God does not produce in those “justified” people (before and after the cross) an experiential righteousness that is not “filthy rags.” In fact, He does; and this righteousness is precious to God and is required, not as the ground of our justification (which is the righteousness of Christ only), but as an evidence of our being truly justified children of God.
Future Grace, p. 151.