English: “All the fat that is upon the innards” — R’ Yishmael says: to include the fat on the stomach (keivah); R’ Akiva says: to include the fat on the small intestines. Just as the fat that covers the innards has a membrane and peels easily, so too every fat that has a membrane and peels easily.
In Sifra / Chullin: The doubled language expands the offered fats beyond the covering membrane. The tannaim differ on the borderline cases (stomach vs intestines), but agree that only membranous, peelable fat is taken for the altar.
Type of Learning
R’ Yishmael / R’ Akiva dispute (scope of “all the fat upon the innards”).
What Is Learned
Shelamim (and parallel) fat offerings include only the classic peelable membrane fats; the tannaitic debate fixes the precise boundaries of the stomach and intestinal layers.