2,338. The Three Kinds of Forbidden Fats

Maachalos Assuros 7:5

One is liable to kareis for three kinds of forbidden fat: the fat around the digestive system, on both kidneys and on the flanks. The fat-tail, however, may be eaten; it is only considered a forbidden fat when it comes to sacrifices, just like the kidneys and the large lobe of the liver, which are also called “fat” in the context of sacrifices. The same is true of “the fat of the land” (Genesis 45:18) and “wheat, fat like kidneys” (Deut. 32:14), which just refers to their quality. Since these things are being taken from the sacrifice to be offered to God, they are called “cheilev” (which literally means fat but refers to the best part) because there’s nothing better than the part offered to God. This is why, regarding terumas maaser, Numbers 18:30 says “When you raise its fat from it.”

Maachalos Assuros 7:6

“The fat around the digestive system” refers to the fat on the abdomen and belly. One is liable for the fat on the inside of the thigh joints; this is the fat “on the flanks.” There’s also fat on the abomasum that’s curved like an arch; this is prohibited. There’s a tendon that stretches like a lobe, which is permitted. The strands of forbidden fats are prohibited but one does not incur kareis for eating them.