In vv. 1-9 the psalmist's cry is chiefly for pardon; in vv. 10-12 he prays chiefly for purity; in vv. 13-17 he vows grateful service. Vv. 18, 19, are probably a later addition. The psalm begins with at once grasping the character of God as the sole ground of hope. That character has been revealed in an infinite number of acts of love. The very number of the psalmist's sins drove him to contemplate the yet greater number of God's mercies. For where but in an infinite placableness and loving-kindness could he find pardon? If the Davidic authorship is adopted, this psalm followed Nathan's assurance of forgiveness, and its petitions are the psalmist's efforts to lay hold of that assurance. The revelation of God's love precedes and causes true penitence. Our prayer for forgiveness is the appropriation of God's promise of forgiveness. The assurance of pardon does not lead to a light estimate of sin, but drives it home to the conscience. The petitions of vv. 1, 2, teach us how the psalmist thought of sin. They are all substantially the same, and their repetition discloses the depth of longing in the suppliant. The language fluctuates between plural and singular nouns, designating the evil as "transgressions" and as "iniquity" and "sin." The psalmist regards it, first, as a multitude of separate acts, then as all gathered together into a grim unity. The single deeds of wrong-doing pass before him. But these have a common root; and we must not only recognise acts, but that alienation of heart from which they come--not only sin as it comes out in the life, but as it is coiled round our hearts. Sins are the manifestations of sin. We note, too, how the psalmist realises his personal responsibility. He reiterates "my"--"_my_ transgressions, _my_ iniquity, _my_ sin." He does not throw blame on circumstances, or talk about temperament or maxims of society or bodily organisation. All these had some share in impelling him to sin; but after all allowance made for them, the deed is the doer's, and he must bear its burden. The same eloquent synonyms for evil deeds which are found in Psalm xxxii. occur again here. "Transgression" is literally _rebellion_; "iniquity," _that which is twisted_ or _bent_; "sin," _missing a mark_. Sin is rebellion, the uprising of the will against rightful authority--not merely the breach of abstract propriety or law, but opposition to a living Person, who has right to obedience. The definition of virtue is obedience to God, and the sin in sin is the assertion of independence of God and opposition to His will.