Leviticus 13:37
But if the scall be in his sight at a stay, and that there is black hair grown up therein; the scall is healed, he is clean: and the priest shall pronounce him clean. But if the scall be in his sight at a stay, and that there is black hair grown up therein; the scall is healed, he is clean: and the priest shall pronounce him clean.
The scall is judged healed when in appearance it is at a stay and no longer spreading, and black hair has grown up in it, and then the diseased person is healed and clean, and the priest shall pronounce him clean after seeing the visible signs of cleanliness. That bodily cleansing under the law of cleansing, which required visible signs of cleanliness before the person could be declared clean, is distinct from the later cleansing of the sanctuary with blood. The laws about leprosy present this horrible, loathsome disease as a fitting type and picture of sin as a moral and mortal disease.
As represented by leprosy, sin is a widespread, infectious, inwardly rooted disease that human means cannot cure. As pictured by leprosy, sin as a moral disease does not heal by itself and can spread its corrupting influence to others. Cleansing from this sin comes through the blood of Christ. Christ's healing of leprosy shows his power to heal mortal sin.
The verse belongs to admirable laws concerning leprosy which show that although God is the healer, he also required his people to take proper precautions. The verse is part of the laws of sanitation promulgated by Moses, which still stand at the head of sanitary law and remain unsurpassed by modern knowledge, proving the divine inspiration that guided Moses. The loathsome leprosy still prevalent in the Holy Land is the same type that existed in scriptural days, and so bears witness to scriptural truth.