In Christ alone
Do not bring your servant into judgment, for no one living is righteous before you. Psalm 143.2
Psalm 143 is the last of the 7 Penitential Psalms all of which, except for 102 and 130, are specifically attributed to David and associated with his rape and murder of Bathsheba and Uriah respectively. It begins with a plea for mercy and a confession of sin. There is no doubting David's guilt, nor does he deny it. His appeal to the fallenness of all humanity is not an attempt to share the blame so much as an acknowledgment of humankind's helplessness to save ourselves from the divine judgment we deserve.
David's plea - "Do not bring your servant into judgment" - anticipates God's intervention through Jesus, who enters creation in order to take the punishment we deserve and then, through his death and resurrection, to secure our salvation and eternal life, which he offers to all as a gift. David lived a thousand years before Christ and so the forgiveness he experienced in answer to this prayer is like the deposit which guarantees God's fulfilment of David's anticipation.
Here is another example of the extraordinary way in which the Bible works. Across the Testaments - Old and New - God's plan of redemption is revealed. Trying to explain it through the tools of academic criticism alone is insufficient. Indeed, assuming that we can sit over Holy Scripture in this way is arrogant and will lead us dangerously astray. Instead we need to sit under The Bible and, in due humility and faith, let speak to us of God's unique love for all creation and of his glorious purposes for us in Christ through the power of the Holy Spirit. Then we can hear its message and respond accordingly.