Parashas Terumah · Passuk 25:4
Yerushalmi Kilayim 9:1 — “shani tola'as” is interpreted through a living creature, and the same principle is extended to other materials derived from living creatures.
English: Just as “shani tola'as” refers to something that has the breath of life, so too any material that has the breath of life.
What Is Learned: The Yerushalmi derives a requirement from “tola'as shani” that the relevant material comes from something living.