Leviticus 13:25
Then the priest shall look upon it: and, behold, if the hair in the bright spot be turned white, and it be in sight deeper than the skin; it is a leprosy broken out of the burning: wherefore the priest shall pronounce him unclean: it is the plague of leprosy.
The priest was to examine a bright spot breaking out where a burn had been, and if the hair in the spot had turned white and the spot appeared deeper than the skin, he was to declare it leprosy broken out of the burning and pronounce the person unclean. This direction belongs to the detailed laws regulating uncleanness and leprosy, which treat leprosy as a contagious disease requiring proper sanitary precautions even while God is acknowledged as the healer. Those Mosaic laws of sanitation still stand at the head of all sanitary law, and their enduring superiority proves that divine inspiration guided their giving.
The same law belongs to the law of cleansing, under which an object had to be made visibly clean before it could receive the sanctuary's cleansing by blood. It is part of the Levitical sanctuary service, whose yearly round forms a pattern typifying Christ's ministry in the heavenly sanctuary. The leprosy so examined is a horrible and loathsome disease, set forth as a fitting type and picture of sin as a dreadful and terrible moral disease embracing every kind of evil thing and mortal sin.
Like that leprosy, sin is incurable by human means and never gets well of itself, being infectious and destructive, rooted within, and producing outward shame, so that cleansing comes only with the help of the great Physician and displays Christ's power to heal. As leprosy spreads, so sin is contagious, for the sinner contaminates the very atmosphere about him, introduces pollution where before there was comparative purity, and by his society leads others into sin, giving more reason to fear such influence than to fear infection from a leper. The leprosy the priest identifies thus points to sin as a dreadful disease needing healing, whose lesson is that the proud self must die and the old person be put off in order to be healed.
The laws given to ancient Israel of which this direction is part belong to a work of cleansing that calls the remnant not to turn away from cleansing truths, including health reform, but to become clean vessels prepared to receive God's Spirit and the latter rain. The same loathsome disease here described remains as prevalent in the Holy Land as in scriptural days, bearing witness to scriptural truth.