TT #273 · Parshas Tazria · Aliyah 7 · Passuk 49
English: and the lesion is greenish or reddish in the garment, leather, warp or woof, or any leather article, it is a lesion of tzaraas and shall be shown to the priest.
Torah Temimah cites Sifra (Toras Kohanim) for the inclusion of garment cases across the rich/poor distinctions.
Sifra — Vayikra 13, Midrash Sefer
English: The Sifra considers garments that can be used by both rich and poor, only the rich, only the poor, or neither, and derives the cases included from the wording of the verse.
Textual derivation
The rule is not limited to garments shared by rich and poor; the Sifra tests the scope across each of these cases.