Leviticus 6:9-10

9“Give Aaron and his sons this command: ‘These are the regulations for the burnt offering: The burnt offering is to remain on the altar hearth throughout the night, till morning, and the fire must be kept burning on the altar.

10The priest shall then put on his linen clothes, with linen undergarments next to his body, and shall remove the ashes of the burnt offering that the fire has consumed on the altar and place them beside the altar.