Parashas Metzora · Passuk 15:32
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “This is the Torah of the zav … and one from whom shichvas zera goes out” — this teaches that a zav who had only one sighting immerses and may eat his Pesach in the evening, like a baal keri.
Single sighting = evening impurity
Chazal treat a single zav sighting like keri: impurity until evening, not the full seven-day zivah structure.