TT #178 · Parshas Tazria · Aliyah 5 · Passuk 27
English: The priest shall examine him on the seventh day. If the lesion has spread in the skin, the priest shall pronounce him unclean; it is a tzaraas affliction.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:27
Torah Temimah cites Sifra (Toras Kohanim) for applying the parallel rules of boil and burn to one another.
Sifra — Vayikra 13, Midrash Sefer
English: The rules stated for a boil apply to a burn, and those stated for a burn apply to a boil.
Textual derivation
A rule stated for a boil also governs a burn, and a rule stated for a burn also governs a boil, so the parallel lesions share the relevant criteria.