Leviticus 6:9-10

9“Command Aaron and his sons, saying, ‘This is 1the law for the burnt offering: the burnt offering itself shall remain on the hearth on the altar all night until the morning, and 2the fire on the altar is to be kept burning on it.

10The priest is to put on 3his linen robe, and he shall put on linen undergarments next to his 4body; and he shall take up the fatty ashes to which the fire 5reduces the burnt offering on the altar and place them beside the altar.