Charles Ellicott Commentary Leviticus 3:5

"And Aaron`s sons shall burn it on the altar upon the burnt-offering, which is upon the wood that is on the fire: it is an offering made by fire, of a sweet savor unto Jehovah." — Leviticus 3:5 (ASV)

And Aaron’s sons. —After the offerer has killed the victim, taken out the choice parts and offered them to the officiating priest, the latter is to burn it, that is, the whole collection of the fat pieces described in Leviticus 3:3-4, upon the ashes of the continual burnt offering, which was the daily offering of the lamb. It always took precedence and burned the whole day (Leviticus 6:12). Besides these choice pieces which therefore had to be burned, the breast and the right shoulder were reserved for the priest, while the remainder of the peace offering was eaten by the offerer, his family, and his friends (Leviticus 7:15–16).