Commentary for Leviticus 20:25

והבדלתם בין הבהמה הטהרה לטמאה YE SHALL THEREFORE DISTINGUISH BETWEEN CLEAN BEASTS AND UNCLEAN — It is needless for Scripture to say that one should distinguish between a cow and an ass for these are different and are therefore distinguishable. But it means: you shall distinguish between such an animal as is clean (permitted) to you and such as is unclean (forbidden) to you although it is a clean animal per se, i.e., make a distinction between an animal which has been killed by cutting at least the greater part of each organ (the gullet and the windpipe) or whether it has been killed by cutting exactly the half of each organ. And how much difference is there between the greater part and the exact half? A hair’s breadth only (and consequently the command is given: והבדלתם, “you shall very carefully distinguish”) (Sifra, Kedoshim, Chapter 12 20; cf. also Rashi on Leviticus 11:47 and Chullin 27a).

ולא תשקצו את נפשותיכם בבהמה ובעוף ובכל אשר תרמוש האדמה, from all kinds of “impure” living creatures אשר הבדלתי לכם, from the ritually “pure.”

Pure for you. Explanation: Pure or impure through your action. For example, if one slaughtered the whole gullet and only half the windpipe it is impure; if one slaughtered the whole gullet and most of the windpipe it is pure. I.e., you made it pure for eating.