When God brings us under conviction, he shows us how far short of his standard we fall. His law searches our hearts. It demands from us love for God and all his commandments, but when we look within, we see resentment at such a high standard, and we see within us a reluctance to comply. Furthermore the Holy Spirit shows us the impossibility of our keeping God’s law, because of the presence of sin within us. There is a perversity, a twistedness, within us, that is like a defective bow. Every time you pull it back to fire an arrow, it twists in your hands. And even if we were able to obey God today – which we are not – how could we take away the guilt of sins that lie in the past? Our record of sin is on display in heaven. We can never go back and put things right, and the consequences of what we have done extends into the eternal future.
How hard mankind finds it to understand this. He hears God commanding him to keep the law, and he immediately thinks that means he is capable of doing so. It never occurs to him that God is teaching him just how sinful he is, and how far short he falls. We are very resistant to this message, and the way God has to teach us is to go and attempt to do what we ought to do, in order to discover our own sinfulness. It never occurs to us that this is the primary reason that the law has been given to man in his fallen state: not to present us with a viable path to heaven, but to teach us the awful truth about our own nature.