Leviticus 13:55
And the priest shall look on the plague, after that it is washed: and, behold, if the plague have not changed his colour, and the plague be not spread; it is unclean; thou shalt burn it in the fire; it is fret inward, whether it be bare within or without.
Leviticus 13:55 belongs to the laws regulating uncleanness and leprosy and bodily cleanliness under the Mosaic law, specifically the instructions in Leviticus 13:48-59 for a priest to examine disease in woven cloth made of warp and woof for garments. It directs that after washing, if the plague has not changed its color and has not spread, it is still unclean and must be burned in the fire. These instructions on leprosy are sanitary directions for dealing with contagious and infectious disease, including infectious germs left in buildings. The verse belongs to the law of cleansing that required an object to be visibly clean before it could undergo the sanctuary's cleansing by blood, so that physical uncleanness had to be removed first, while the sanctuary's later cleansing addressed moral defilement.
Leprosy is a horrible and dreadful disease that serves as a fitting type, picture, and prefigure of sin as a moral disease. As presented in Leviticus 13-14, leprosy is incurable and infectious, consumes its victim, has its chief seat within, pollutes the source of life, and brings outward shame, while likewise sin affects the heart as well as appearing in visible acts, does not heal by itself, and can spread its pollution to others. The plague that remains unchanged after washing and must be burned represents a deep-seated, inward infection that washing cannot remove, pointing to the need for sin to be removed, and no one is free from sin's infection except those who seek help from Christ, whose blood cleanses sin.
Israel's instructions about clean and unclean conditions serve as examples connected with cleansing and health reform for practicing physical and spiritual purity. Applied to pride, the verse teaches the death of pride and the putting off of the old self. In dress it calls Christians to reject pride, vanity, and worldly fashions and to dress distinctly, because wearing them misrepresents the Lord and can spread pride and vanity among weaker believers.