TT #218 · 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 limit on a priest’s power to declare purity contrary to the objective signs.
Sifra — Vayikra 13, Midrash Sefer
English: If the verse said only “the priest shall pronounce him pure,” one might think a priest’s mistaken declaration could make an impure person pure. The verse first states “he is pure,” so the priest’s declaration confirms actual purity rather than creating it.
Textual derivation
The priest’s declaration must agree with the objective signs: he cannot make an impure person pure merely by saying so.