The Burnt offering: Required to Be: Entirely Burned
Source: TTT
Leviticus 1:8, 9, 12, 13
Then Aaron’s sons the priests are to arrange the pieces, including the head and the fat, atop the burning wood on the altar. / The entrails and legs must be washed with water, and the priest shall burn all of it on the altar as a burnt offering, an offering made by fire, a pleasing aroma to the LORD. / He is to cut the animal into pieces, and the priest shall arrange them, including the head and fat, atop the burning wood that is on the altar.
Leviticus 6:9
“Command Aaron and his sons that this is the law of the burnt offering: The burnt offering is to remain on the hearth of the altar all night, until morning, and the fire must be kept burning on the altar.