TT #30 · Parshas Tazria · Aliyah 1 · Passuk 4
English: She shall remain thirty-three days in the blood of her purification; she shall touch no consecrated thing and shall not enter the sanctuary until her days of purification are completed.
Chabad.org — Chumash, English translation + Rashi for Vayikra 12:4
Torah Temimah cites Sifra (Toras Kohanim).
Daat — Sifra (Toras Kohanim) on Vayikra 12
English: “And thirty days and three days” — one might reason that since the female has more days of impurity, she should also have more days of purity; Scripture establishes the prescribed period for a male.
Explicit textual limitation
The Sifra rejects a simple symmetry between the periods of impurity and purity: the longer impurity period following the birth of a girl does not imply a longer purification period for a boy.