13:1-17 The plague of leprosy was an uncleanness, rather than a disease. Christ is said to cleanse lepers, not to cure them. Common as the leprosy was among the Hebrews, during and after their residence in Egypt, we have no reason to believe that it was known among them before. Their distressed state and employment in that land must have rendered them liable to disease. But it was a plague often inflicted immediately by the hand of God. Miriam's leprosy, and Gehazi's, and king Uzziah's, were punishments of particular sins; no marvel there was care taken to distinguish it from a common distemper. The judgment of it was referred to the priests. And it was a figure of the moral pollutions of men's minds by sin, which is the leprosy of the soul, defiling to the conscience, and from which Christ alone can cleanse. The priest could only convict the leper, (by the law is the knowledge of sin,) but Christ can cure the sinner, he can take away sin. It is a work of great importance, but of great difficulty, to judge of our spiritual state. We all have cause to suspect ourselves, being conscious of sores and spots; but whether clean or unclean is the question. As there were certain marks by which to know it was leprosy, so there are marks of such as are in the gall of bitterness. The priest must take time in making his judgment. This teaches all, both ministers and people, not to be hasty in censures, nor to judge anything before the time. If some men's sins go before unto judgment, the sins of others follow after, and so do men's good works. If the person suspected were found to be clean, yet he must wash his clothes, because there had been ground for the suspicion. We have need to be washed in the blood of Christ from our spots, though not leprosy spots; for who can say, I am pure from sin?

2. When a man shall have in the skin, &c.—The fact of the following rules for distinguishing the plague of leprosy being incorporated with the Hebrew code of laws, proves the existence of the odious disease among that people. But a short time, little more than a year (if so long a period had elapsed since the exodus) when symptoms of leprosy seem extensively to have appeared among them; and as they could not be very liable to such a cutaneous disorder amid their active journeyings and in the dry open air of Arabia, the seeds of the disorder must have been laid in Egypt, where it has always been endemic. There is every reason to believe that this was the case: that the leprosy was not a family complaint, hereditary among the Hebrews, but that they got it from intercourse with the Egyptians and from the unfavorable circumstances of their condition in the house of bondage. The great excitement and irritability of the skin in the hot and sandy regions of the East produce a far greater predisposition to leprosy of all kinds than in cooler temperatures; and cracks or blotches, inflammations or even contusions of the skin, very often lead to these in Arabia and Palestine, to some extent, but particularly in Egypt. Besides, the subjugated and distressed state of the Hebrews in the latter country, and the nature of their employment, must have rendered them very liable to this as well as to various other blemishes and misaffections of the skin; in the production of which there are no causes more active or powerful than a depressed state of body and mind, hard labor under a burning sun, the body constantly covered with the excoriating dust of brick fields, and an impoverished diet—to all of which the Israelites were exposed while under the Egyptian bondage. It appears that, in consequence of these hardships, there was, even after they had left Egypt, a general predisposition among the Hebrews to the contagious forms of leprosy—so that it often occurred as a consequence of various other affections of the skin. And hence all cutaneous blemishes or blains—especially such as had a tendency to terminate in leprosy—were watched with a jealous eye from the first [Good, Study of Medicine]. A swelling, a pimple, or bright spot on the skin, created a strong ground of suspicion of a man's being attacked by the dreaded disease.

then he shall be brought unto Aaron the priest, &c.—Like the Egyptian priests, the Levites united the character of physician with that of the sacred office; and on the appearance of any suspicious eruptions on the skin, the person having these was brought before the priest—not, however, to receive medical treatment, though it is not improbable that some purifying remedies might be prescribed, but to be examined with a view to those sanitary precautions which it belonged to legislation to adopt.