Parashas Metzora · Passuk 15:13
Chabad.org — English translation + Rashi
Torah Temima points to Megillah 8a.
English: “From his flux and he shall count” — this teaches that a zav of two sightings requires a count of seven [clean days].
Two-sighting zav requires seven days
Chazal require the seven-day count even for a zav of only two sightings (though the sacrifice requires three).