Parashas Metzora · Passuk 15:02
Chabad.org — English translation + Rashi
Torah Temima points to Niddah 55a (verified on the daf).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “His discharge is tamei” — this teaches that the discharge itself is tamei.
Intrinsic impurity of the fluid
Chazal establish that the zov fluid is itself a primary source of tumah.