Deliver me from the guilt of bloodshed, O God, you who are God my Saviour, and my tongue will sing of your righteousness. Psalm 51.14
King David's confession rendered him a new man. Gone are the lust and egotism which led him into heinous crimes and sin against God. In his brokenness he has rediscovered humility and faith. With them, his desire to worship and serve return. Although there are 5 more verses until the end of the Psalm, verse 14 (above) is probably David's own conclusion, with the rest being added later.
According to the original Hebrew, the "guilt of bloodshed" extends beyond the shedding of (innocent) blood to encompass belonging to a society which tolerates undeserved suffering. Likewise, the salvation of God includes the opportunity God affords his people to become agents of reconciliation ourselves. Finally, singing of God's righteousness is an expression of the Psalmist's restored priority, to use every ounce of his being to testify to the mercy and power of God who has rescued him from sin and despair.
The doxology, which may have been appended to this Psalm, is replete with familiar phrases and memorable images. It refers to the rebuilding of Jerusalem following the exile in Babylon and to the rededication of the temple in 516BC, exactly 70 years after it was destroyed - just as Jeremiah the prophet had foretold! So, in this one Psalm, we are invited to marvel at the way God restores individuals and whole nations.