Midrasz do Kapłańska 3:16

3) ("And he shall present …) the fat that covers the innards and all the fat that is on the innards": (This is written five times.) What is the intent of this? Because it is written (Ibid. 3:16): ("And the Cohein shall smoke …) all the fat for the L–rd. (17): … All fat and all blood you shall not eat… (Vayikra 7:25): For all who eat fat of the beast of which one presents a fire-offering to the L–rd, the soul that eats shall be cut off from its people" — I might think that even the wall-fat (the fat of the heart, the chest, and the throat) is included (in the interdict against eating fat); it is, therefore, written: "the fat that covers the innards (the entrails)." I might think that it (eating wall-fat) is not subject to the punishment (kareth), but that it is subject to the exhortation; it is, therefore, written (again): "the fat that covers the innards." would then exclude only the (wall-) fat of chullin, but not that of a consecrated animal; it is, therefore, written (again): "the fat that covers the innards" (i.e., only that fat is intended.) I might think that it (eating the wall-fat of a consecrated animal) is not subject to the punishment, but that it is subject to the exhortation; it is, therefore, written (again): "the fat that covers the innards." I might think that it is not subject to the exhortation and that it is subject to sacrifice (if he so wishes, even though he may eat it); it is, therefore, written (for the fifth time): "the fat that covers the innards" (Only that fat is to be sacrificed.)

4) (Vayikra 3:16): "And the Cohein shall smoke them": all at once. "the bread of a fire-offering for a sweet savor, all the fat for the L–rd": to include fat in me'ilah (the interdict against abuse of sacred objects).

5) It was said in the name of R. Yishmael: It is written (Bamidbar 18:17): But the bechor (the first-born) of an ox, or the bechor of a sheep, or the bechor of a goat, you shall not redeem. They are consecrated. Their blood shall you sprinkle upon the altar and their fat shall you smoke.": This teaches us that a bechor requires blood and fats upon the altar. Whence do we derive the same for ma'aser and pesach? From (Devarim 12:27): "And the blood of your sacrifices shall be spilled on the altar of your G d (first), and (then) the flesh shall you eat." This tells me only of their blood. Whence do I derive (the same for) their fat? From (Vayikra 3:16): "all the fat for the L–rd."