Psalm 51:2
"Wash me throughly from mine iniquity, and cleanse me from my sin."
It is easy to pass over the time frame from David's sin with Bathsheba to the time when the Prophet Nathan approached him. Close to a year had passed from the time that David committed adultery to the time his sin was revealed, and in that one year sin had taken a toll on David. This is why David said, "Wash me throughly from mine iniquity, and cleanse me from my sin." David knew the affect of sin on his life, and he wanted them completely removed.