Parashas Metzora · Passuk 15:25
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “Not in the time of her niddah” — upon her niddah, adjacent to her niddah; from where [do we include] distant from her niddah? Scripture teaches “or when she flows”; and from where to include the eleven [days]? Scripture teaches “not in the time of her niddah.”
Eleven-day zivah window
Chazal establish the classic structure: seven niddah days followed by an eleven-day window in which further sightings create zavah status.