[Psalm 51 is perhaps the most famous and heartfelt prayers of sorrow ever written. King David committed adultery and compounded that sin by murdering the husband of the woman he ousted after. This is said to be his plea for mercy.]
Have mercy on me, God, in your kindness.
In your compassion blot out my offense.
O wash me more and more from my guilt
and cleanse me from my sin.
My offenses truly I know them;
my sin is always before me.
Against you, you alone, have I sinned;
what is evil in your sight I have done.
That you may be justified when you give sentence
and be without reproach when you judge.
O see, in guilt was I born,
a sinner was I conceived.
Indeed you love truth in the heart;
then in the secret of my heart teach me wisdom.
O purify me, then I shall be clean;
O wash me, I shall be whiter than snow.
Make me hear rejoicing and gladness,
that the bones you have crushed may revive.
From my sins turn away your face
and blot out all my guilt.
A pure heart create for me,
O God, put a steadfast spirit within me.
Do not cast me away from your presence,
nor deprive me of your holy spirit.
Give me again the joy of your help;
with a spirit of fervor sustain me,
that I may teach transgressors your ways
and sinners may return to you.
O rescue me, God, my helper, and
my tongue shall ring out your goodness.
O Lord, open my lips
and my mouth shall declare your praise.
For in sacrifice you take no delight,
burnt offering from me you would refuse;
my sacrifice, a contrite spirit.
A humbled, contrite heart you will not spurn.
In your goodness, show favor to Zion:
rebuild the walls of Jerusalem.
Then you will be pleased with lawful sacrifice,
holocausts offered on your altar.
— From A Catholic Prayer Book
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