Leviticus 3:5
And Aaron’s sons shall burn it on the altar upon the burnt sacrifice, which is upon the wood that is on the fire: it is an offering made by fire, of a sweet savour unto the LORD. And Aaron’s sons shall burn it on the altar upon the burnt sacrifice, which is upon the wood that is on the fire: it is an offering made by fire, of a sweet savour unto the LORD.
Leviticus 3:5 belongs to the instructions for the peace offering within the sacrificial system given to Israel. Peace offerings were an expression of thanksgiving to God and were presented in great numbers when the people assembled at the annual feasts. The offering was presented to the Lord with prayer for acceptance and blessing, with a portion set aside for a sacred shared meal. In that meal the priest received the breast and the right shoulder with some minor parts, and those who brought the offering ate the remainder.
The fat was to be separated first and burned on the altar as an offering to God Himself and never eaten, before the priest took what he desired. The directions were made most exact because appetite and covetous desire for gain could lead a priest to appropriate what was solemnly devoted to the Lord. This is what Hophni and Phinehas did by taking flesh by force before the fat had been separated.
The outward ritual was not a meaningless form but was designed to point beyond itself to Christ's ministry and death as the great Sacrifice that would take away the sins of the world. Properly observed, this worship encouraged genuine devotion, kindness, and sympathy rather than mere ceremony or self-gratification.