Wash me throughly from mine iniquity - literally, "Multiply to wash me." The word rendered "throughly" is a verb, either in the infinitive or imperative mood, and suggests the idea of "multiplying" or "increasing." The reference is to that which might need constant or repeated washings in order to remove a stain adverbially to denote intensity, or thoroughness. On the word wash as applicable to sin, see the notes at Isaiah 1:16.

And cleanse me from my sin - Remove it entirely. Make me wholly pure. See the notes at Isaiah 1:16. In what manner he hoped that this would be done is shown in the following portions of the psalm. It was -

(a) by forgiveness of the past, Psalm 51:9; and

(b) by making the heart pure and holy through the renewing and sanctifying influences of the Holy Spirit, Psalm 51:10-11.

Wash me throughly - הרבה כבסני harbeh cabbeseni, "Wash me again and again, - cause my washings to be multiplied." My stain is deep; ordinary purgation will not be sufficient.

Wash me thoroughly from mine iniquity,.... Which supposes defilement by sin, and that very great, and such as none can remove but the Lord himself; who, when he takes it in hand, does it effectually and thoroughly; see Ezekiel 36:25. David's sin had long lain upon him, the faith of it had as it were eaten into him, and spread itself over him, and therefore he needed much washing: "wash me much", all over, and thoroughly:

and cleanse me from my sin: which only the blood of Christ can do, 1 John 1:7. The psalmist makes use of three words to express his sin by, in this verse Psalm 51:1; which signifies "rebellion", as all sin has in it rebellion against God the lawgiver, and a contempt of his commandments; "perverseness", "crookedness", sin being a going out of the plain way of God's righteous law; and "a missing the mark"; going besides it or not coming up to it: and these he makes rise of to set forth the malignity of sin, and the deep sense he had of the exceeding sinfulness of it; and these are the three words used by the Lord in Exodus 34:7; when he declares himself to be a sin forgiving God; so that David's sin came within the reach of pardoning mercy.

Wash me {c} throughly from mine iniquity, and cleanse me from my sin.

(c) My sins strike so fast in me, that I have need of some singular kind of washing.

2. Wash me-Purity as well as pardon is desired by true penitents.

51:1-6 David, being convinced of his sin, poured out his soul to God in prayer for mercy and grace. Whither should backsliding children return, but to the Lord their God, who alone can heal them? he drew up, by Divine teaching, an account of the workings of his heart toward God. Those that truly repent of their sins, will not be ashamed to own their repentance. Also, he instructs others what to do, and what to say. David had not only done much, but suffered much in the cause of God; yet he flees to God's infinite mercy, and depends upon that alone for pardon and peace. He begs the pardon of sin. The blood of Christ, sprinkled upon the conscience, blots out the transgression, and, having reconciled us to God, reconciles us to ourselves. The believer longs to have the whole debt of his sins blotted out, and every stain cleansed; he would be thoroughly washed from all his sins; but the hypocrite always has some secret reserve, and would have some favorite lust spared. David had such a deep sense of his sin, that he was continually thinking of it, with sorrow and shame. His sin was committed against God, whose truth we deny by wilful sin; with him we deal deceitfully. And the truly penitent will ever trace back the streams of actual sin to the fountain of original depravity. He confesses his original corruption. This is that foolishness which is bound in the heart of a child, that proneness to evil, and that backwardness to good, which is the burden of the regenerate, and the ruin of the unregenerate. He is encouraged, in his repentance, to hope that God would graciously accept him. Thou desirest truth in the inward part; to this God looks, in a returning sinner. Where there is truth, God will give wisdom. Those who sincerely endeavour to do their duty shall be taught their duty; but they will expect good only from Divine grace overcoming their corrupt nature.