Create in me a pure heart, O God, and renew a steadfast spirit within me. Psalm 51:10 NIV
In this psalm David has recorded for us his horrified discovery of the depths of his depravity.
I think before this experience he had been pretty complacent with himself: he was basically a good man and other people could be good too if they would just apply themselves.
Now this! He was a sinner! In fact, he now knows sin was in his DNA from the moment the sperm met the egg in his mother’s womb. What a great discovery, one that all too many of us never make. We think of our sins as unfortunate slips rather than outward expressions of a fundamentally perverse nature. But David now knows that goodness, real goodness – a heart wholly for God* and a spirit forever fixed on Him – is not a matter of a simple choice. Rather, it requires radical surgery – a divine act of creation and starting over again, renewing. Without that, all his former “goodness” was just a matter of personality, as little to his credit as eye color.
Had he been “a man after God’s own heart” (1 Sam 13:14) before this? Yes, I think so, but it had been simply a matter of choice. But from here on it was a reality as never before – a divine work and not a human one.
*The Heb. word is tahor, often translated “clean.” It has the connotation of being all one thing, totally unmixed.
Called To Be Transformed 