But we are all as an unclean thing, and all our righteousness are as filthy rags. Isa. 64:6.
Because we are born separated from God when we come into this world, we are all partakers of the common problem of self-centeredness. Sometimes people look at a newborn baby and ponder, How could such a tiny person be a sinner? He has never had a chance to break the commandments. How could he be a sinner? But if you recognize that sin's number-one manifestation is self-centeredness, it is a little easier to understand. Newborn babies are certainly self-centered! They're the most openly self-centered people around! Never mind if mother is sleeping or eating or trying to do something else. When baby wants something, he wants it now!
Another problem people sometimes face is how they can be sinning by continuing to live their life on their own, apart from God, so long as they are good, moral people. We have tended to define sin in terms of doing bad things, and if we are strong-willed enough to refrain from doing bad things, we think that we have righteousness.
The apostle Paul admitted that he was the chief of sinners. Did that mean that his life was immoral, that he was the chief of criminals? No, it meant that he had come close enough to the Lord Jesus to recognize his true condition. He recognized that the only righteousness he had came from Jesus, and that apart from Him he had none at all.
It is a hard thing to realize that even our good deeds can be sin if we are living apart from the faith relationship with Christ. It is difficult to admit that "all our righteousness are as filthy rags." The text doesn't say that all our filthy rags are as filthy rags, or that all our iniquities are as filthy rags. That we could accept more easily. No, all our righteousness, all our rightdoing, all our so-called obedience, that is done apart from Christ, is still filthy rags, is still sin.
It is the motives and desires on the inside that God looks at, not our outward appearance. We may mow the widow's lawn, in itself a good deed, but apart from Christ it is sin, because our motive will inevitably be a selfish one. True obedience is always from the heart, and comes only through relationship with Christ.