Leviticus 4:8
6 The priest must dip his finger in the blood and sprinkle some of it seven times before the Lord toward the front of the special curtain of the sanctuary. 7 The priest must put some of the blood on the horns of the altar of fragrant incense that is before the Lord in the Meeting Tent, and all the rest of the bull’s blood he must pour out at the base of the altar of burnt offering that is at the entrance of the Meeting Tent. 8 “‘Then he must take up all the fat from the sin-offering bull: the fat covering the entrails and all the fat surrounding the entrails, 9 the two kidneys with the fat on their sinews, and the protruding lobe on the liver (which he is to remove along with the kidneys) 10 —just as it is taken from the ox of the peace-offering sacrifice—and the priest must offer them up in smoke on the altar of burnt offering.
Sirach 47:2
Ben Sira, Ecclesiasticus1 After him Nathan rose up to prophesy in the days of David. 2 As the fat is set apart from the offering of well-being, so David was set apart from the Israelites. 3 He played with lions as though they were young goats, and with bears as though they were lambs of the flock. 4 In his youth did he not kill a giant, and take away the people's disgrace, when he whirled the stone in the sling and struck down the boasting Goliath?
Notes and References
"... In 47:2, Ben Sira shows his exemplary knowledge of the Scriptures by making use of the verbal root on (Hiphil / Hophal). According to priestly legislation, fat was to be set apart from the meat offerings. Eating the fat of the sacrificed animals was not allowed, but as the most valuable part of the offering, the fat had to be burned in an offering to God. The technical term referring to the separating of the fat from the sacrifice is the verb on. (Compare Exodus 29:13; Leviticus 2:9; 3:3-5; 9-11, 14-16, 4:8-19) It is no wonder that Ben Sira leans on priestly language, as he stresses cultic issues of all sorts whenever he has a chance to focus on them. Aaron surpasses Moses in the length of presentation when Ben Sira devotes himself to a meticulous description of Aaron's priestly vestments (Sirach 45:6-13). Furthermore, Ben Sira emphasizes that an eternal covenant was made with Aaron and his offspring (45:15). God himself was Aaron's legacy (45:22) ..."
Marttila, Marko Foreign Nations in the Wisdom of Ben Sira: A Jewish Sage between Opposition and Assimilation (p. 185) De Gruyter, 2012