ייִדישער מחשבֿה אויף במדבר 19:6

The uncleanness through leprosy we have already explained. Our Sages have also clearly stated the meaning thereof. All agree that leprosy is a punishment for slander. The disease begins in the walls of the houses (Lev. 14:33, seq.). If the sinner repents, the object is attained: if he remains in his disobedience, the disease affects his bed and house furniture: if he still continues to sin, the leprosy attacks his own garments, and then his body. This is a miracle received in our nation by tradition, in the same manner as the effect of the trial of a faithless wife (Num. v. ii, seq.). The good effect of this belief is evident. Leprosy is besides a contagious disease, and people almost naturally abhor it, and keep away from it. The purification was effected by cedar-wood, hyssop, scarlet thread, and two birds (Lev. 14:4); their reason is stated in various Midrashic sayings, but the explanation does not agree with our theory. I do not know at present the reason of any of these things; nor why cedar-wood, hyssop, and scarlet were used in the sacrifice of the red heifer (Num. 19:6); nor why a bundle of hyssop was commanded for the sprinkling of the blood of the Passover-lamb (Exod. 12:22). I cannot find any principle upon which to found an explanation why these particular things have been chosen.