Charles Ellicott Commentary Psalms 51:2

"Wash me thoroughly from mine iniquity, And cleanse me from my sin." — Psalms 51:2 (ASV)

Wash me thoroughly.

Literally, Wash me much, whether we follow the Hebrew text or the Hebrew margin. The two clauses of the verse are not merely antithetic.

The terms wash and cleanse seem to imply, respectively, the actual and the ceremonial purification. The former term literally means to tread, describing the process of washing clothes (as blankets are washed to this day in Scotland) by trampling them with the feet. The latter term is used for the formal declaration of cleanliness by the priest in the case of leprosy (Leviticus 13:6–34).

(For the terms iniquity and sin, see Psalms 32:1.)