Chabad.org — English translation + Rashi
Torah Temimah points to Chullin 93a.
E-Daf.com — Chullin 93a
HebrewBooks / Shas PDF
English: Rav Yehudah said in the name of Shmuel: Fat on the omasum and the reticulum is forbidden and punished with kares — and that is “the fat that is on the innards.”
Identification of specific organ fats — chelev on the masas and beit ha-kosot is the biblical forbidden fat of the innards.
Chelev on the masas (omasum) and beit ha-kosot (reticulum) is the biblical forbidden fat of the innards. Shmuel’s statement both prohibits that fat under penalty of kares and equates it with the phrase “the fat that is on the innards” in the verse. The ruling supplies a practical anatomical identification of the chelev that the Torah requires to be removed and offered.