TT #133 · Parshas Tazria · Aliyah 2 · Passuk 13
English: When the priest sees that the eruption has covered the whole body, he shall pronounce the affected person clean; when it has all turned white, that person is clean.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:13
Torah Temimah cites Sifra (Toras Kohanim) for the requirement that the eruption cover the entire body for this rule.
Sifra — Vayikra 13, Midrash Sefer
English: Alternatively, “all his flesh” teaches that the eruption must spread over the whole body.
Textual derivation
“All his flesh” means the eruption must spread over the entire body.