ויקרא, פרק י״ג, פסוק י״ז

The purification process of a person suffering from a skin affliction takes a surprising turn when the mark spreads to cover their entire body. At the very moment the affliction achieves complete physical coverage, the person achieves purity. The principle that an individual becomes pure when the affliction blooms across their whole body is a universal rule. It applies to all types of skin afflictions, covering any situation where prior impurity is resolved specifically through the complete spreading of the mark [תורה תמימה, מלבי״ם, אדרת אליהו].

Physically, this transformation means the skin of the affected area has changed its color [ביאור שטיינזלץ], which includes developing a specific dull white appearance [רש״ר הירש]. Once this total change occurs, the person is considered entirely pure. This status remains intact even if the white color appears, fades away, and then returns [פירושי רד״צ הופמן].

The primary approach among commentators highlights a crucial limitation to this law. This unique purity applies only when the affliction spreads progressively across the body. It explicitly excludes a person who arrives before the priest with their entire body already covered in white from the very beginning. If the mark appears everywhere all at once rather than through a gradual spread, the person is not pure. Instead, they remain impure and must be quarantined due to the large scale of the affliction.