TT #245 · Parshas Tazria · Aliyah 7 · Passuk 45
English: As for the person afflicted with tzaraas, his garments shall be torn, his head shall be unkempt, he shall cover his upper lip, and he shall call out, “Impure! Impure!”
Torah Temimah cites Moed Katan 5a for this teaching on the metzora’s public conduct and ritual status.
English: Rabbi Abbahu derives from “impure, impure, he shall call out” that impurity itself calls to the public: “Keep away, keep away.”
Textual derivation
The metzora must publicly announce his impurity so that others keep their distance.