Leviticus 13:10
And the priest shall see him: and, behold, if the rising be white in the skin, and it have turned the hair white, and there be quick raw flesh in the rising; And the priest shall see him: and, behold, if the rising be white in the skin, and it have turned the hair white, and there be quick raw flesh in the rising;
The priest's examination turns on three marks together: a white rising in the skin, hair turned white, and quick raw flesh in the rising. The direction belongs to the law of cleansing in Leviticus 12-15, where the affected person or object had to be made visibly clean first before the sanctuary could be cleansed with blood, making it part of a prior outward purification distinct from the sanctuary's deeper cleansing. The directions for identifying and controlling leprosy give sanitary instruction about contagious diseases, including diseases that leave infectious germs in buildings, providing practical precautions even though God is the healer and showing that God required cleanliness and obedience to health-related laws.
Those Mosaic laws for examining and controlling leprous disease still stand at the head of sanitary law above modern medical knowledge and enforcement, which proves divine inspiration guided Moses. Leprosy is a fitting type and prefigure of sin as a terrible moral and mortal dreadful disease, and the disease described in Scripture was still prevalent in the Holy Land. As represented by leprosy, sin is widespread, infectious, and by human means incurable, never getting well of itself, corrupting the inner life while bringing outward shame.
Sin includes not only wrong acts but the motives, purposes, and desires of the heart, and like leprosy it is contagious: the sinner contaminates the very atmosphere, introduces pollution where all before was comparative purity, and leads others to sin by his society, an influence more to be feared than the infection of the leper. Leprosy was acknowledged as an incurable disease, so the leper's cleansing was regarded as a miracle comparable to raising the dead. Cleansing depended on faith in the cleansing power of God, the Author of the ceremonies, with the rites showing faith in Christ; cleansing comes through the blood of Christ for those who repent and believe, and Jesus Christ showed his power to heal this type of mortal sin. Healing from the disease of sin requires the proud old self to die, putting off the old person and putting on the new and becoming humble enough to receive God's kingdom like a little child.