TT #298 · Parshas Tazria · Aliyah 7 · Passuk 57
English: If it appears again in the garment, warp or woof, or any leather article, it is a spreading lesion; you shall burn it in fire.
Torah Temimah cites Sifra (Toras Kohanim) for the gris-sized minimum for a recurrent lesion.
Sifra — Vayikra 13, Midrash Sefer
English: Might any amount of recurrence count? “Again” teaches that the second lesion, like the first, must be at least a gris in size.
Textual derivation
A recurrent lesion must meet the minimum gris-sized measure, just as the original lesion did.