Psalm 51:1-12
English Standard Version (ESV)
Create in Me a Clean Heart, O God
To the choirmaster. A Psalm of David, when Nathan the prophet went to him, after he had gone in to Bathsheba.
51 Have mercy on me, O God,
according to your steadfast love;
according to your abundant mercy
blot out my transgressions.
2 Wash me thoroughly from my iniquity,
and cleanse me from my sin!
3 For I know my transgressions,
and my sin is ever before me.
4 Against you, you only, have I sinned
and done what is evil in your sight,
so that you may be justified in your words
and blameless in your judgment.
5 Behold, I was brought forth in iniquity,
and in sin did my mother conceive me.
6 Behold, you delight in truth in the inward being,
and you teach me wisdom in the secret heart.
7 Purge me with hyssop, and I shall be clean;
wash me, and I shall be whiter than snow.
8 Let me hear joy and gladness;
let the bones that you have broken rejoice.
9 Hide your face from my sins,
and blot out all my iniquities.
10 Create in me a clean heart, O God,
and renew a right[b] spirit within me.
11 Cast me not away from your presence,
and take not your Holy Spirit from me.
12 Restore to me the joy of your salvation,
and uphold me with a willing spirit.

David is asking God to make him clean… he is not saying… I will do X, Y, or Z to become clean…
But only by God’s washing and regeneration can he be clean. God used the prophet Nathan to point out his Sin.

We have the law to point out our sin and condemn us to death. (for the wages of sin is death)
We have the Gospel, that is, Christ pulled us out of the grave, he washed us clean, and he feeds us through his word. All this he does because he loves you, so that you shall not perish but have eternal life!