TT #36 · Parshas Tazria · Aliyah 1 · Passuk 4
English: She shall sit out thirty-three days in the blood of purification; she shall touch no sacred thing and shall not enter the sanctuary until the days of her purification are complete.
Chabad.org — Chumash, English translation + Rashi for Vayikra 12:4
Torah Temimah cites Zevachim 32b.
E-Daf — Zevachim 32b · Shas.org
English: Ulla said in the name of Reish Lakish: an impure person who inserted his hand inside is liable for lashes. The comparison teaches that just as partial touching is considered touching, partial entry is considered entry.
Textual comparison
Even partial entry into the Sanctuary is treated as entry for the prohibition.