Psalms 51:7

Purge me with hyssop Or, as with hyssop; the note of similitude being frequently understood. As lepers, and other unclean persons, are by thy appointment purified by the use of hyssop and other things, Leviticus 14:6; Numbers 19:6; so do thou cleanse me, a most leprous and polluted creature, by thy grace, and by the virtue of that blood of Christ, which is signified by those ceremonial usages. The word

תחשׂאני, techatteeni, here rendered purge me, properly means, expiate my sin. “The psalmist well knew that his sins were too great to be expiated by any legal purifications, and therefore prays that God would himself expiate them, and restore him; that is,” not only remove their guilt, but “make him as free from those criminal propensities to sin, and from all the bad effects of his aggravated crimes, as though he had been purified from a leprosy, by the water of cleansing, sprinkled on him by a branch of hyssop; and that he might be, if possible, clearer from all the defilement and guilt of sin than the new fallen snow. I think both these senses are included in the expiation which the psalmist prays for; as the person whose leprosy was expiated was wholly cured of his disease, and freed from all the incapacities attending it.” Dodd.