Halakha Imamat 6:6: Mishneh Torah, Positive Mitzvot, Mishneh Torah, Negative Mitzvot & Sefer HaChinukh

To keep fire always burning on the altar of the burnt-offering, as it is said, “The fire shall ever be burning on the altar” (Lev. 6:6).

Not to mount the altar by steps, as it is said, “Neither shalt thou go up by steps unto mine altar” (Ex. 20:26).

Not to extinguish the fire on the altar, as it is said, “Fire shall ever be burning upon the altar, it shall never go out” (Lev. 6:6).