Parashas Metzora · Passuk 15:32
Chabad.org — English translation + Rashi
Torah Temima points to Rav Huna.
English: “This is the Torah of the zav” — Rav Huna said: A zav’s first sighting conveys impurity even under duress, as it is stated “This is the Torah of the zav and one from whom shichvas zera goes out” — just as shichvas zera conveys impurity under duress, so a zav’s first sighting conveys impurity under duress.
First sighting even under ones
Chazal distinguish: the first sighting of a zav is impure even if forced; later sightings that complete zivah status require non-forced emission.