TT #115 · 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 general minimum size standard for tzaraas lesions.
Sifra — Vayikra 13, Midrash Sefer
English: “Tzaraas” establishes a general rule for tzaraas: its minimum measure is a gris.
Textual derivation
The Sifra treats a gris-sized area as the general minimum measure for the laws of tzaraas.