Leviticus 3:3

And he shall offer of the sacrifice of the peace-offering an offering made by fire unto the Lord, certain parts of the animal offered for the purpose of establishing a closer fellowship with God were to be burned on the altar of burnt offering; the fat that covereth the inwards, the large net of adipose membrane in the abdominal cavity, and all the fat that is upon the inwards, that which is only loosely attached to the intestines and may be peeled off without difficulty,