TT #212 · Parshas Tazria · Aliyah 5 · Passuk 37
English: If the netek remains unchanged and black hair has grown in it, the netek is healed; he is clean, and the priest shall pronounce him clean.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:37
Torah Temimah cites Sifra (Toras Kohanim) for the wording that describes the netek as remaining unchanged.
Sifra — Vayikra 13, Midrash Sefer
English: “If it remained in his eyes”—this could refer only to the priest’s own assessment. How do we know the rule also applies when the netek appears unchanged to the priest’s son or student? The verse says, “If the netek remained in his eyes,” extending the rule beyond the priest’s own assessment.
Textual derivation
The wording “in his eyes” is interpreted broadly enough to include the assessment of the person’s son or student, not only the afflicted person’s own view of the lesion.