The penitent's plea for pardon.
"Have mercy," etc. This psalm is like a page of autobiography written in the author's life-blood. It is, indeed, the utterance of what Psalms 51:17 describes, "a broken and a contrite heart." Nowhere in the Old Testament Scriptures do we find so profound depth and tenderness of penitence, joined with such childlike faith in God's pardoning mercy. If the dark record of David's crime had been silently omitted, we should have been utterly at a loss to understand this psalm. Who could have thought that from the same harp which uttered the sweet strain of Psalms 23:1-6, could proceed so deep a wail of grief and self-abasement? Yet it is just because David's joy in God and love to God were so real that his repentance was so bitter. No hypocrite could have penned this psalm. Any one who calls David a hypocrite shows dense ignorance of human nature.
I. THE PENITENT'S PLEA FOR PARDON. "According to thy loving-kindness [or, 'mercy']; according to the multitude of thy tender mercies [or, 'compassions'.]." He has nothing to plead in defence or palliation. God's mercy and pity are his sole hope. What warrant has he to expect them? Answer: God's covenant with Israel. Such sins as David's (murder and adultery) could not be purged by sacrifice (see Hebrews 10:28). And while under the condemnation of such guilt, it would have been vain presumption to offer peace offerings. Verse 16 may include both. But the whole law of sacrifice revealed God's delight in mercy, while it foreshadowed the true atonement. The gospel puts this plea in our mouth in a new form. It supplies an incomparably more glorious warrant and encouragement than the Old Testament believer possessed—the atonement which God himself has provided (2 Corinthians 5:21; Ephesians 1:7; Romans 5:8).
II. THE UNLIMITED EFFICACY OF THIS PLEA. It is difficult to imagine sins more heinous than those of which David had been guilty. Their guilt was enormously aggravated by the fact that he was the divinely chosen king of the chosen people, an inspired prophet, and the object of signal and unrivalled blessings from God. Perhaps we have sometimes wished this dark page of Scripture had remained unwritten. But there it stands, to teach us that no sinner need despair of God's mercy. The door at which David entered is wide enough for every true penitent. So St. Paul points to his own case as an encouragement to all (1 Timothy 1:15, 1 Timothy 1:16).
III. THE EXCLUSIVE ADEQUACY OF THIS PLEA. It admits no addition, no partnership, no substitute. It is this or none (Romans 3:23-26). By one sin, St. James teaches us, God's Law is as completely broken as by many (James 2:10). Therefore only the blood which cleanses from all sin (1 John 1:7) can cleanse from any (Titus 3:4-7). In the heavenly world there will be immense differences in glory and happiness, according to attainment and service. But in this respect—the ground of pardon and salvation—all stand on one level; all join in one song (Revelation 1:5, Revelation 1:6; Revelation 5:9).
The folly and guilt of impenitence appear most of all in this—that it is a despising of God's mercy and compassion (Romans 2:4).