The 112th mitzvah is that we are commanded to make a metzora recognizable so that people should keep away from him.

The source of this commandment is G‑d's statement1 (exalted be He), "A metzora who has on himself a mark of tzora'as, must tear his clothing, go without a haircut, cover his face down to his lips; and he shall call out, 'Unclean! Unclean!' "

The proof2 that this counts as a positive commandment is from the Sifri, which says, "From the verse3 [regarding a kohen gadol], 'He shall not let his hair grow long nor tear his garments,' I would think that it is forbidden even if he has tzora'as. How would I explain the statement [that a metzora], 'must tear his clothing, go without a haircut'? — As referring to everyone except a kohen gadol. The Torah therefore writes [the extra phrase4], 'who has on himself a mark of tzora'as,' — to tell you that even a kohen gadol 'must tear his clothing' and must 'go without a haircut' [if he has tzora'as]."

It is clear that it is a Biblical prohibition for a kohen gadol to tear his clothing or go without a haircut.5 And the general rule is,6 "When you have a positive commandment and a prohibition: if both can be kept, that is best; if not, the positive commandment overrides the prohibition." Since a kohen gadol who is stricken with tzora'as does tear his clothing and grow his hair long, it proves that it must be a positive commandment.7

It has been passed down through the Oral Tradition that people who carry other forms of tumah must also make themselves recognizable in order that people keep away from them. The Sifra says, "Those who are tameh meis; who have had relations with a woman in a state of niddah [and are thereby tameh]; and all others who could make another person tameh — how do we know [that they too must make themselves recognizable]? From the phrase, 'he shall call out, 'Unclean! Unclean!' "

This means that any person who is tameh must proclaim that he is tameh,8 i.e. to make a sign to show that he is tameh and will convey tumah to anyone who touches him, in order that people should keep away from him.

We have already explained that not all the signs9 for recognizing a metzora are obligatory for women. This is derived from the statement of our Sages,10 "A man must grow his hair and tear his clothing, and a woman must not grow her hair and tear her clothing." She does, however, cover her face down to her lips11 and proclaim that she is tameh, like other people who are tameh.