TT #244 · 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 15a for this teaching on the metzora’s public conduct and ritual status.
English: “He shall cover his upper lip”—the Sages interpret this as keeping the lips closed, like a person under a ban or in mourning; this is associated with the restriction on exchanging greetings.
Textual derivation
The covering of the lips is interpreted as a sign of separation from ordinary social greetings.