leviticus 13:2 When a man shall have in the skin of his flesh a rising, a scab, or bright spot, and it be in the skin of his flesh like the plague of leprosy; then he shall be brought unto Aaron the priest, or unto one of his sons the priests: - Free Bible Online

      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.

JFB.