ויקרא, פרק י״ג, פסוק כ״ג

Diagnosing leprosy requires a careful distinction between an active, spreading disease and a natural physical reaction to a previous injury. When a bright spot appears over an infected wound or boil, the priest must observe its behavior to determine its status. The primary condition for purity is that the bright spot remains entirely static. While this generally means the blemish stays in its place, commentators note a precise distinction regarding its exact location. The spot must remain strictly within the confined area directly beneath the blemish itself, rather than just in the general vicinity [מלבי״ם, פרדס יוסף, רד״צ הופמן]. This exactness is critical because blemishes can sometimes migrate and shift across the skin [אבן עזרא]. As long as the spot is contained within the borders of the original boil and has not spread to healthy skin or a burn, it does not cause impurity [תורה תמימה, רד״צ הופמן].

Even if the bright spot does not fade in color after a period of quarantine, its lack of movement is the deciding factor. Remaining static proves that the spot is merely a consequence of the underlying boil rather than an independent outbreak of leprosy [חיזקוני, העמק דבר]. In this state, the blemish is identified simply as the scar of the boil. This scar is the visible mark left on the flesh by the heat and inflammation of the original wound, representing a completely natural healing process [רש״י, ביאור שטיינזלץ].

The terminology used for this scar describes the drying, shrinking, and wrinkling of the skin specifically caused by heat or fire [מלבי״ם, הכתב והקבלה]. It signals the beginning of recovery as the skin calms, forming a thin, dry crust—often compared to a garlic peel—that covers the open wound [רש״י, תורה תמימה, ביאור יש״ר]. Some connect this concept to the idea of joining and solidifying; unlike a destructive fire, this heat creates new connective tissue to mend the wound [רש״ר הירש]. For the priest to confirm this diagnosis, the scarred area must be clearly noticeable, yet not to the extent that it completely obscures the original location of the boil [תורה תמימה, אדרת אליהו].

When finalizing the diagnosis, the legal ruling is structured so that the reason is given before the actual declaration of purity. This reversed order establishes a strict requirement: the priest is only permitted to declare the person pure if he is absolutely certain that the blemish is merely the scar of the boil. If any doubt remains, purity cannot be declared [מלבי״ם, תורה תמימה, רד״צ הופמן]. Ultimately, the directive to declare purity applies directly to the afflicted person, clearing them of the condition, rather than referring to the bright spot itself [ברכת אשר].