TT #231 · Parshas Shemini · Aliyah 7 · Passuk 39
Chabad.org — Vayikra Chapter 11 with Rashi
English: “Yours for food”: this includes an eight-month premature animal, whose slaughter does not render it pure.
Shabbos 136a.
E-Daf.com — Shabbos 136a (Tsurras Hadaf)
Textual inclusion — The Chazal derives the stated rule from the wording and comparison in the verse.
An eight-month premature animal is included because slaughter does not purify it.