TT #93 · Parshas Tazria · Aliyah 1 · Passuk 5
English: On the seventh day the priest shall conduct an examination, and if the affection has remained unchanged in color and the disease has not spread on the skin, the priest shall isolate them for another seven days.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:5
Torah Temimah cites Sifra (Toras Kohanim) for the requirement that the seventh-day examination occur in daylight.
Sifra — Vayikra 13, Midrash Sefer
English: “On the seventh day” — by day, not at night.
Temporal qualification
The examination described for the seventh day must take place during daylight.