The fire shall be kept burning on the altar continually; it must not be extinguished.

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.

Leviticus 6:12
The fire on the altar shall be kept burning; it must not be extinguished. Every morning the priest is to add wood to the fire, arrange the burnt offering on it, and burn the fat portions of the peace offerings on it.

Leviticus 6:14
Now this is the law of the grain offering: Aaron's sons shall present it before the LORD in front of the altar.

Ezekiel 40:46
and the chamber that faces north is for the priests who keep charge of the altar. These are the sons of Zadok, the only Levites who may approach the LORD to minister before Him."

The fire shall ever be burning on the altar; it shall never go out.