Parashas Metzora · Passuk 15:03
Chabad.org — English translation + Rashi
Torah Temima points to Niddah 43b (verified on the daf).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “From his discharge” — even part of his discharge is tamei; this teaches that a zav of two sightings already conveys tumah to a bed or a seat.
Two sightings for mishkav/moshav
Chazal teach that two emissions are sufficient to render the zav capable of conveying tumah to objects on which he lies or sits.