Psalm 51

Have mercy on me, O God,
according to your steadfast love;
according to your abundant mercy
blot out my transgressions.
(Psalm 51:1 ESV)

....

"What's actually true is that when I come to the Lord after I've blown it, I've only one argument to make. It's not the argument of the difficulty of the environment that I am in. It's not the argument of the difficult people that I'm near. It's not the argument of good intentions that were thwarted in some way. No, I have only one argument. It's right there in the first verse of Psalm 51, as David confesses his sin with Bathsheba. I come to the Lord with only one appeal, his mercy. I've no other defense. I've no other standing. I've no other hope. I can't escape the reality of my biggest problem - me! So I appeal to the one thing in my life that's sure and will never fail. I appeal to the one thing that guaranteed not only my acceptance with God, but the hope of new beginnings and fresh starts. I appeal on the basis of the greatest gift I ever have or ever will be given. I leave the courtroom of my own defense, I come out of hiding, and I admit who I am. But I'm not afraid, because I've been personally and eternally blessed. Because of what Jesus did, God looks on me with mercy. It's my only appeal; it's the source of my hope; it's my life. Mercy, mercy me!"

- Paul David Tripp, Whiter than Snow