Restore to me the joy of your salvation,
and uphold me with a willing spirit.
Then I will teach transgressors your ways,
and sinners will return to you.
I've always found this part of Psalm 51 to be the boldest part of David's repentance. David the adulterer, David the murderer, David the weaver of massive government and military conspiracies... this big sinner prayed this bold prayer. He had fully repented, and then he confidently asks God for joy again and offers to teach other sinners how to turn to God!
David had to know the gracious heart of God to make this requests, for if God had no grace toward the repentant King, this would have been an arrogant and presumptive request! Really, how could David the big time sinner teach sinners repentance? It would be like North Korea teaching democracy to the world. Except David's sin was forgiven because David really had repented. And with that forgiveness was restoration of relationship with God.
I learn from David to be bold in my repentance. I see Your grace is big enough to not only cover my sin, but to fully forgive me, and You will restore my heart to You. You let repentant sinners teach other sinners how to return to You, otherwise there would be no practical way for the gospel to go forward. That means You will use me. Thank You, Lord!