“And the L-RD spoke unto Moses and unto Aaron, saying: When a man shall have in the skin of his flesh a rising, or a scab, or a bright spot, and it become in the skin of his flesh the plague of leprosy [tzara’ath], then he shall be brought unto Aaron the [Kohein] priest, or unto one of his sons the [kohanim] priests.”
– Leviticus 13:1-2, JPS 1917 Tanach
The so-called “plague of leprosy,” as mentioned in the Tanach, is not exactly the leprosy of more modern times. Rather, it is a category of various skin diseases that needed to be determined by the Kohein: for only the Kohein has the authority to make the pronouncement. “And the [kohein] priest shall look on him, and pronounce him unclean” (Leviticus 13:3, JPS).
The leprosy of biblical times was the result of spiritual malaise, most commonly said to be the result of lashon harah (literally, evil tongue, otherwise known as a specific type of gossip). The Hebrew word, metzorah is a contraction of two words: motzi ra, that refer to a person one spreads slander (Arachin 15b). The very visible physical malaise is meant to show the person that he needs to correct his ways. In other words, the outward sign is meant to compel him to do teshuvah (repentance).
Sin may be manifest in our lives, living below the surface of our awareness. For this reason, one must make an attempt to examine one’s life. There are visible signs, at times, that we need to understand as wake-up calls. Also, when the children O Israel entered the land, sometimes they found mold in the walls, so they would have to dig out the mold. While on the one hand, the nega (plague) in the form of mold should serve for them to search their conscience, on the other hand, they often found hidden treasures in the walls, hidden by the previous occupants, the Caananites, who hoped to return. There is always a reward for rectifying our faults.