http://www.hopeofchrist.net/2010/08/psalm-51/
...He prays for washing. He knows he is filthy. He understands the stench of his sin and is not satisfied to ask to be washed once but pleads with God to wash him thoroughly, to cleanse him from his sin.
The stain of his sin is deep. He can not flee from the terror of his own conscience and has nowhere to take his conscience and implores God to take away the filth that he bears.
There is no therapy here. There is nothing of David trying to learn to integrate his mistakes and learn to love himself anyway. He understands that soothing words of encouragement from his friends telling him that he’s OK will not do. He needs a thorough cleansing from the very God who has every right to judge David for the filth of his sin.
Verse 3 is the refrain of a man who knows his sin: For I know my transgressions.
David is not merely saying that he remembers everything he did. What he’s wrestling with in Verses 3 through 6 is how horrible sin is and the gulf that exists between a sinner and a holy God. I want you to remember one thing as we move along through this Psalm: We will never seriously beg God for pardon until we have understood sin in such a way that it inspires fear in us. If sin has never evoked terror to our souls then we cannot understand the sweetness of pardon that is in the Gospel.
Beloved, many of us don’t know what the true issue with sin is and so Verse 4 adds something that is foreign to us. David says: “Against you, you only, have I sinned and done what is evil in your sight.”
Most of us want to stop David right here. What are you talking about David? It wasn’t God who you looked at while bathing. It wasn’t God who you got pregnant. You didn’t send God with a letter to be killed in battle. You didn’t get God involved in any of these sins. How can you claim that you only sinned against God? Have you forgotten about Bathsheba, Uriah, Joab, and the entire nation that could have been brought down by your selfish sins?!
The issue here is that David understands something profound about sin. He understands that the whole world could pardon him of any trouble for his sin but it will provide no relief before the bar of God’s justice.
In James 2:10-11, James notes something very important about sin that David underscores here. First, James says something strange to our ears in verse 10: 10 For whoever keeps the whole law but fails in one point has become accountable for all of it.
Do you see what James is saying? We could be so perfect as to keep every part of the Law of God and fail at one point and be guilty before the whole Law. That doesn’t seem to make any sense until James explains what he means in verse 11: 11 For he who said, “Do not commit adultery,” also said, “Do not murder.” If you do not commit adultery but do murder, you have become a transgressor of the law.
I don’t know if you can see what has just been said but James testifies with the rest of the Word of God that the real issue with sinning against the Law is that, when we sin, we sin against a holy, eternal God. If it’s even at the seemingly smallest point, our sin amounts to raising our hand in rebellion against the God of the universe. We commit treason with every small sin and every sin is just cause for God to condemn us.
David understands the weight of this rebellion and so he reminds God in the second part of verse 4 that God is justified and blameless in His judgment against sin. He’s not coming to God arrogantly and telling God that He must forgive him but He understands that God would be perfectly just to condemn sin for what it is....
