The main grounds on which the Davidic authorship of this psalm is denied are four. First, it is alleged that its conceptions of sin and penitence are in advance of his stage of religious development; or, as Cheyne puts it, "David could not have had these ideas" ("Aids to Dev. Study of Crit.," 166). The impossibility depends on a theory which is not yet so established as to be confidently used to settle questions of date. Again, the psalmist's wail, "Against Thee only have I sinned," is said to be conclusive proof that the wrong done to Bathsheba and the murder of Uriah cannot be referred to. But is not God the correlative of sin, and may not the same act be qualified in one aspect as a crime and in another as a sin, bearing in the latter character exclusive relation to God? The prayer in ver. 18 is the ground of a third objection to the Davidic authorship. Certainly it is hopeless to attempt to explain. "Build the walls of Jerusalem" as David's prayer. But the opinion held by both advocates and opponents of David's authorship, that vv. 18, 19, are a later liturgical addition, removes this difficulty. Another ground on which the psalm is brought down to a late date is the resemblances in it to Isa. xl.-lxvi., which are taken to be echoes of the prophetic words. The resemblances are undoubted; the assumption that the psalmist is the copyist is not.
The personified nation is supposed by most modern authorities to be the speaker; and the date is sometimes taken to be the Restoration period, before the rebuilding of the walls by Nehemiah (Cheyne, "Orig. of Psalt.," 162); by others, the time of the Babylonish exile; and, as usual, by some, the Maccabean epoch. It puts a considerable strain upon the theory of personification to believe that these confessions of personal sin, and longing cries for a clean heart, which so many generations have felt to fit their most secret experiences, were not the wailings of a soul which had learned the burden of individuality, by consciousness of sin, and by realisation of the awful solitude of its relation to God. There are also expressions in the psalm which seem to clog the supposition that the speaker is the nation with great difficulties—e.g., the reference to birth in ver. 5, the prayer for inward truth in ver. 6, and for a clean heart in ver. 10. Baethgen acknowledges that the two latter only receive their full meaning when applied to an individual. He quotes Olshausen, a defender of the national reference, who really admits the force of the objection to it, raised on the ground of these expressions, while he seeks to parry it by saying that "it is not unnatural that the poet, speaking in the singular, should, although he writes for the congregation, bring in occasional expressions here and there which do not fit the community so well as they do each individual in it." The acknowledgment is valuable; the attempt to turn its edge may be left to the reader's judgment.
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.
Not less profound is that other name, which regards sin as "iniquity" or distortion. Then there is a straight line to which men's lives should run parallel. Our life's paths should be like these conquering Roman roads, turning aside for nothing, but going straight to their aim over mountain and ravine, stream or desert. But this man's passion had made for him a crooked path, where he found no end, "in wandering mazes lost." Sin is, further, missing an aim, the aim being either the Divine purpose for man, the true Ideal of manhood, or the satisfaction proposed by the sinner to himself as the result of his sin. In both senses every sin misses the mark.
These petitions show also how the psalmist thought of forgiveness. As the words for sin give a threefold view of it, so those for pardon set it forth in three aspects. "Blot out";—that petition conceives of forgiveness as being the erasure of a writing, perhaps of an indictment. Our past is a blurred manuscript, full of false and bad things. The melancholy theory of some thinkers is summed up in the despairing words, "What I have written, I have written." But the psalmist knew better than that; and we should know better than he did. Our souls may become palimpsests; and, as devotional meditations might be written by a saint on a parchment that had borne foul legends of false gods, the bad writing on them may be obliterated, and God's law be written there. "Wash me thoroughly" needs no explanation. But the word employed is significant, in that it probably means washing by kneading or beating, not by simple rinsing. The psalmist is ready to submit to any painful discipline, if only he may be cleansed. "Wash me, beat me, tread me down, hammer me with mallets, dash me against stones, do anything with me, if only these foul stains are melted from the texture of my soul." The psalmist had not heard of the alchemy by which men can "wash their robes and make them white in the blood of the Lamb"; but he held fast by God's "loving-kindness," and knew the blackness of his own sin, and groaned under it; and therefore his cry was not in vain. An anticipation of the Christian teaching as to forgiveness lies in his last expression for pardon, "make me clean," which is the technical word for the priestly act of declaring ceremonial purity, and for the other priestly act of making as well as declaring clean from the stains of leprosy. The suppliant thinks of his guilt not only as a blotted record or as a polluted robe, but as a fatal disease, the "first-born of death," and as capable of being taken away only by the hand of the Priest laid on the feculent mass. We know who put out his hand and touched the leper, and said, "I will: be thou clean."
The petitions for cleansing are, in ver. 3, urged on the ground of the psalmist's consciousness of sin. Penitent confession is a condition of forgiveness. There is no need to take this verse as giving the reason why the psalmist offered his prayer, rather than as presenting a plea why it should be answered. Some commentators have adopted the former explanation, from a fear lest the other should give countenance to the notion that repentance is a meritorious cause of forgiveness; but that is unnecessary scrupulousness. "Sin is always sin, and deserving of punishment, whether it is confessed or not. Still, confession of sin is of importance on this account—that God will be gracious to none but to those who confess their sin" (Luther, quoted by Perowne).