Breathe in me,  O Holy Spirit, that my thoughts may all be holy. Act in me, O Holy Spirit, that  my work, too, may be holy. Draw my heart, O Holy Spirit, that I love but what  is holy. Strengthen me, O Holy Spirit, to defend all that is holy. Guard me,  then, O Holy Spirit, that I always may be holy. Amen.

–Augustine

Have mercy on me, God, in your goodness
in your abundant compassion
blot out my offense.
Wash away all my guilt;
from my sin cleanse me.
 
For I know my offense;
 my sin is always before me.
Against you alone have I sinned;
 I have done such evil in your sight
That you are just in your sentence,
 blameless when you condemn.
True, I was born guilty,
 a sinner, even as my mother conceived me.
Still, you insist on sincerity of heart;
 in my inmost being teach me wisdom.
 
Cleanse me with hyssop, that I may be pure;
 wash me, make me whiter than snow.
Let me hear sounds of joy and gladness;
 let the bones you have crushed rejoice.
Turn away your face from my sins;
 blot out all my guilt.
 
A clean heart create for me, God;
 renew in me a steadfast spirit.
Do not drive me from your presence,
 nor take from me your holy spirit.
Restore my joy in your salvation;
 sustain in me a willing spirit.
 
I will teach the wicked your ways,
 that sinners may return to you.
Rescue me from death, God, my saving God,
 that my tongue may praise your healing power.
Lord, open my lips;
 my mouth will proclaim your praise.
For you do not desire sacrifice;
 a burnt offering you would not accept.
My sacrifice, God, is a broken spirit;
 God, do not spurn a broken, humbled heart.
 
–Psalm 51:3-19 (Prayer for Repentance)