The Hymn "God Be Merciful to Me" is based off of Psalm 51 and the first verse reads:
"God, be merciful to me; on thy grace I rest my plea.
Plenteous in compassion thou, blow out my transgressions now;
wash me, make me pure within; Cleanse, o cleanse me from my sin."
God has washed us from our sin, because he is full of compassion FOR US SINNERS.