Repentance for sin and serving Christ go hand in hand, such that you cannot repent for sin unless you are a servant of Christ, and you cannot serve Christ unless you repent for sin. Generations of Christians have understood this, for the first command our Savior ever gave was, “Repent and believe in the gospel” (Mark 1:15). And throughout all generations, believers have turned to Psalm 51 for assistance in expressing their repentance to the Lord.
As the superscript to Psalm 51 tells us, this psalm was prompted by David’s response “when Nathan the prophet went to him, after he had gone in to Bathsheba.” When the words of God came to David through the prophet Nathan, David turned from his sin (2 Sam. 12:1–15a). This is in keeping with how the Lord works faith in our hearts. Just as faith comes by the hearing of the Word of God (Rom. 10:17), so does repentance, for repentance is inseparable from faith. We must turn from sin in repentance unto Christ in faith. Moreover, that David, God’s chosen king, was required to heed God’s revelation through an old covenant prophet means we have no excuse for ignoring God’s command to repent given by Jesus the Messiah. Augustine of Hippo comments on today’s passage, “An exalted king heard a prophet, let His humble people hear Christ.”
As far as David’s prayer of repentance itself, we should notice the way that he casts himself wholly on the mercy of our Creator. David does not approach God arrogantly or demand pardon as if it were somehow owed to Him. Instead, he casts himself on the “abundant mercy” of the Lord (Ps. 51:1). Even though David has fallen far, he has not forgotten God’s covenant promise to forgive His repentant people. Indeed, he seeks refuge in the Lord’s revelation of His character as the “God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness” (Ex. 34:6). David does not run away from God after having sinned; rather, He runs to the Lord. He well understands that since his sin is chiefly against his Maker, his only hope for restoration is from God Himself (Ps. 51:4).
David’s sin prompts him to consider the depth of his depravity. His act with Bathsheba was no accident, and he could not excuse it as a momentary lapse in judgment. Instead, it was born out of his innate depravity (v. 5). David sinned because he was a sinner, just as all of us sin because we are born into this world fallen. Our only hope is for the Lord to cleanse us not only of our particular sins, but of our fallenness in Adam.