Leviticus 6:9-10

9Command Aaron and his sons, saying, This is the law of the burnt-offering; this, the burnt-offering, shall be on the hearth on the altar all night unto the morning, and the fire of the altar shall be kept burning on it.

10And the priest shall put on his linen raiment, and his linen breeches shall he put on his flesh, and take up the ashes to which the fire hath consumed the burnt-offering on the altar, and he shall put them beside the altar.