Psalm 51:7 "Cleanse me with hyssop, and I will be clean; wash me, and I will be whiter than snow."
Back in
2 Samuel 11, we saw the story of David and Bathsheba. He committed adultery with her and then sent her husband to the front lines of battle, so that he would die, and it would cover up his sin. Nathan called him out on it, and this Psalm is written along the lines of David's confession. I don't know if it was written at that exact time, or after the fact, as sort of a memoir.
After this confrontation, David no longer tries to hide his offense. He knows it does no good to attempt to cover up one's sin from God. He knows he must absolutely throw himself on God's mercy. He understands that it is only God, and the restoration of their communion that can lift the burden of bloodguilt from David's shoulders. He acknowledges his sin, and that he is by his nature a sinner (since birth, v. 5). He is a dirty man, and needs to be cleansed. Specifically by hyssop. Remember that hyssop is described in
Leviticus 14 as an ingredient for cleansing from infectious skin diseases (sexually transmitted disease, possibly?).
David wants to hear joy and gladness again, rejoicing from the bones God has crushed. He has received his punishment. And when he asks God to hide his face from his sins, I imagine that means something along the lines of, "When you look at me, don't see my sins." Not to ignore them, or pretend they didn't occur. Because they did.
But not only does he ask for forgiveness from this sin, he seems to not want it to happen again. He asks God to create in him a clean heart. A pure heart, and to renew a right spirit in him. He wants this lust problem to be cleared up. He doesn't want women to be a stumbling point for him. I wonder if those who battle addiction to pornography and the other trappings of lust see beyond just needing forgiveness, but also truly desire a pure heart?
He shows then what I consider a mark of leadership, in that he wants to teach others what not to do. He doesn't want them to fall into this sin, I would imagine firstly. And secondly, he doesn't want them to bear the burden of guilt that he feels. David can tell someone, "I've been where you are." He wants to be able to credit God with being his help, and restoring a firm relationship with him.
Again there is a reference to God not really desiring the blood sacrifices in and of themselves, rather a broken spirit and a contrite heart. God would eschew the sacrifice if a person truly came and threw themselves before God, and allowed God to take control of his heart. That's not to say God rebuked those who made the sacrifices. That was simply the demonstration.
Psalm 51 reminds me of:
Create In Me A Clean Heart by Keith Green
Absalom, Absalom by Pierce Pettis