Leviticus 13:2 "When a man shall have on the skin of his flesh..."

A person whose body has the signs of the Tzara'at affliction (see Positive Mitzvah 77), is considered impure. These signs appear as a skin ailment, but Tzara'at is not a physical disease treated by a doctor. Rather, it is the priest, who is dedicated to the service of HaShem, that determines the impurity of these signs. Through his guidance and care, the afflicted person can purify himself.

The priest will help the person with Tzara'at to correct his deeds and remove the cause of his affliction.