Psalm 51
The superscription above Psalm 51 reads:
"A psalm of David. When the prophet Nathan came to him after David had committed adultery with Bathsheba."
Psalm 51 is like a window to King David's guilt over his sins of adultery and murder. David seemed to have lost sight of God, for a little while at least. We can read about it at Second Samuel, chapters 11 & 12.
Had David gone out with his armies in the campaign against the Ammonites as he should have, the whole episode might never have happened and there would have been no Psalm 51. But then neither would there have been a King Solomon (David's son by Bathsheba) - the author of the books of Proverbs, Ecclesiastes, and Song of Songs. So keep in mind, even though we may sin, something good can still come of it if we are repentant.
David begins Psalm 51 with an appeal for forgiveness according to God's faithful love and great mercy. That alone is worth noting for sinners everywhere. David does not deny his guilt, but he openly admits it, recognizing that even though his sins affected others, it was against God, God above all, that he had sinned. Notice all the things David asks of God, then ask: Would God place these things before us in his Word and not be willing to provide them?
Yet you desired faithfulness even in the womb;
You taught me wisdom in that secret place.
Cleanse me with hyssop, and I will be clean;
Wash me, and I will be whiter than snow.
Let me hear joy and gladness;
Let the bones you have crushed rejoice.
Hide your face from my sins
And blot out all my iniquity.
Create in me a pure heart, O God,
And renew a steadfast spirit within me.
Restore to me the joy of your salvation
And grant me a willing spirit, to sustain me.
Then I will teach transgressors your ways,
So that sinners will turn back to you.
-Psalm 51:6-10; 12, 13
God used David at his lowest point in life to draw guilt-ridden sinners to Himself. Psalm 51 is the go-to chapter in the Bible for every person who feels unworthy, empty, or darkened of soul. The treasure of this chapter, the gem to hold on to, is this:
My sacrifice, O God, is a broken spirit;
A broken and contrite heart you, God, will not despise.
-Psalm 51:17
As poetic parallelisms go, verse 17 is a Synthetic parallel, which means the second part neither repeats nor contrasts the first part but adds to and enlarges upon it. Here it means that God's forgiveness is assured for those who regret their past mistakes.