TT #120 · Parshas Tazria · Aliyah 2 · Passuk 10
English: It is chronic leprosy on the skin of his flesh, and the priest shall pronounce him impure; he shall not isolate him, for he is impure.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:11
Torah Temimah cites Sifra (Toras Kohanim) for the rule that an already assigned impure status is not followed by another isolation or definitive declaration.
Sifra — Vayikra 13, Midrash Sefer
English: And from where do we learn that one who is confined is not made definitive and that one who is confined is not confined again? The verse says, “He shall not shut him up, for he is impure”: once a person has been designated with impurity, no further action is required.
Textual derivation
Once the person has a recognized impure status, the priest does not begin a new isolation or repeat a definitive declaration for that same status.