Leviticus 13:42
And if there be in the bald head, or bald forehead, a white reddish sore; it is a leprosy sprung up in his bald head, or his bald forehead. And if there be in the bald head, or bald forehead, a white reddish sore; it is a leprosy sprung up in his bald head, or his bald forehead.
The white-reddish sore appearing in the bald head or bald forehead is leprosy sprung up there, and the law identifies such visible bodily uncleanness under Moses. It belongs to Israel's regulations about uncleanness and leprosy, given as part of a cleansing work whose cleansing truths were not to be abandoned. It was part of the rules for making an unclean person visibly clean before the sanctuary's cleansing with blood, with this physical uncleanness distinct from moral defilement that required atonement. A suspected case was held in quarantine until the condition could be determined, while a confirmed case was counted unclean, cut off by permanent separation from home and friends, defiling whatever was touched, and requiring the warning cry of Unclean, unclean to those approaching. Even though God declared Himself the healer, the laws concerning leprosy required proper precautions.
The chapter belongs to sanitary guidance about contagious diseases and infections, including infectious germs that can remain in buildings. The Mosaic laws of sanitation still stand at the head of all sanitary law, and rigid observance preserves life and prevents disease, as shown when disease deaths were eliminated in the Panama Canal Zone by rigid enforcement of known sanitary laws, with their enduring supremacy proving the divine inspiration that guided Moses.
Leprosy is a horrible, loathsome disease and a fitting type and prefigure of sin, made a type of mortal sin embracing every kind of evil. Like leprosy, sin is incurable by human means and never gets well of itself, infectious and contagious, destructive, rooted within, and a source of outward shame. Sin is the transgression of the law, and all unrighteousness is sin.
Like a leper, the sinner contaminates the very atmosphere and introduces pollution where all before was comparative purity, and his society leads others to sin, so there is more reason to fear sinful influence than infection from a leper. Jesus made leprosy a showing of His power to heal, and the same loathsome leprosy prevalent in scriptural days is still prevalent in the Holy Land, with its continued presence bearing witness to scriptural truth.