Psalms 51:2 - Joseph Benson’s Commentary on the Old and New Testaments

Wash me thoroughly from mine iniquity, &c. “I have made myself exceeding loathsome by my repeated and heinous acts of wickedness, which, like a stain that hath long stuck to a garment, is not easily purged away; but do not, therefore, I beseech thee, abhor me, but rather magnify thy mercy in purifying me perfectly, and cleansing me so thoroughly, that there may be no spot remaining in me.” Bishop Patrick. Hebrew, הרבה כבסני, harbeh chabbeseeni, is literally, multiplica, lava me, multiply, wash me: that is, Wash me very much. By which phrase he implies the greatness of his guilt, the insufficiency of all legal washing, and the absolute necessity of some other and better means of cleansing him from it, even God's grace and the atoning blood of Christ; which as Abraham saw by faith, John 8:56, so did David, as is sufficiently evident (allowance being made for the darkness of the Old Testament dispensation) from divers passages of his Psalms. Observe, reader, sin defiles us, renders us odious in the sight of the holy God, and uneasy to ourselves; it unfits us for communion with God, in grace or glory. But when God pardons sin, he cleanses us from it, so that we become acceptable to him, easy to ourselves, and have liberty of access to him. Nathan had assured David, upon his first profession of repentance, that his sin was pardoned. The Lord has taken away thy sin, thou shalt not die, 2 Samuel 12:13: yet he prays, Wash me, cleanse me, blot out my transgressions; for God will be sought unto, even for that which he has promised; and those whose sins are pardoned, must pray that the pardon may be more and more evidenced to them. God had forgiven him, but he could not forgive himself, and therefore he is thus importunate for pardon as one that thought himself unworthy of it.