Stages of purification

“If an offerer is already pure before coming to the sanctuary, what is there left for a חטאת sacrifice to remove from him/her? As we have seen in ch. 6 above, N. Kiuchi has pointed out that a scale-diseased person is declared pure (טהר) at each of three successive stages of ritual purification (Lev 14:8, 9, 20). This means that he is pure enough for that stage, but his purity at an earlier stage does not make a later stage unnecessary. Significantly, while the first and second stages involve various nonsacrificial rituals, including ablutions, it is the third and highest stage on the eighth day that is achieved through a complex of sacrifices (vv. 10–20), including a purification offering (v. 19). So a purification offering removes a kind of residual impurity that is left even after other means of purification have been carried out.”—Cult and Character, page 176