In comparing with those passages the complaint of Job in 9, 28ff. we observe a very interesting fact. 'I am afraid of all my pains, I know that Thou wilt not hold me guiltless. (29) I shall be condemned; why then do I labor in vain? (30) If I wash myself with snow water, and make my hands never so clean: (31) yet wilt thou plunge me in the ditch, and mine own clothes shall abhor me.' His terrible sufferings convinced Job that GOD regarded him not only as not free from sin and, on account of that, as deserving punishment, but also as a sinner. If, conscious of his freedom from transgressions, Job did his utmost by washing himself in the cleanest water and thereby removed any sin possibly attaching to him, it would be of no avail, as God, by covering his body with leprosy to such an extent that even his garments would detest him, would thereby prove the reverse of his asserted moral purity, his sinfulness. Or should the consideration that God did not in reality dip Job in a ditch full of mire suggest that Job's own alleged washing of himself was merely a figure of speech? At the outset, at least, this much is clear: Job did not refer to any levitical procedure of levitical cleansing, as for such purification snow-water is not superior to running water, Lev. 15, 13, nor is after the immersion of the whole body an additional, special cleansing of the hands prescribed after even the gravest impurity, not even after leprosy.
from page 247, Studies in Sin and Atonement