TT #229 · Parshas Shemini · Aliyah 7 · Passuk 39
Chabad.org — Vayikra Chapter 11 with Rashi
English: “From the animal that is yours for food”: the verse compares impure and pure animals; just as the fetus of a pure animal is pure, so the fetus of an impure animal is pure.
Chullin 70b.
E-Daf.com — Chullin 70b (Tsurras Hadaf)
Analogy — The Chazal derives the stated rule from the wording and comparison in the verse.
The verse compares the fetal rules of impure and pure animals.