Leviticus 6:12

“And the fire upon the altar shall be burning in it, it shall not be put out, etc.] There were three fires, or piles of wood for fire continually; the first was a large one, on which the daily sacrifice was burnt; the second less, and called the pile of the incense, because they took from it fire in a censer to burn the morning and evening incense; and the third was only for preserving the fire that it might not go out: and of this it is written, (<030612>Leviticus 6:12) f141; and Maimonides f142 observes, that some say, the first of these is meant by the burning all night, (<030609>Leviticus 6:9) and the second by the fire of the altar burning in it, (<030612>Leviticus 6:12) but his own…”

“It shall not be put out - The fire coming down from heaven, was to be perpetually preserved, and not suffered to go out, partly that there might be no occasion or temptation to offer strange fire; and partly to teach them whence they were to expect the acceptance of all their sacrifices, even from the divine mercy, signified by the fire that came down from heaven which was an usual token of God's favourable acceptance. Every morning - Though the evening also be doubtless intended, yet the morning is only mentioned, because then the altar was cleansed, and the ashes taken away, and a new fire made. Thereon - Upon the burnt - offering, which thereby would be sooner consumed, that the way might…”

“6:12-13 This passage cautions that the fire on the bronze altar must be constantly tended and never allowed to go out, perhaps anticipating the tragedy of the “wrong kind of fire” offered by Nadab and Abihu (10:1-2).”

“the fire: Lev 9:24; Num 4:13, Num 4:14; Mar 9:48, Mar 9:49; Heb 10:27 burn wood: Lev 1:7-9, Lev 3:3-5, Lev 3:9-11, Lev 3:14-16; Exo 29:38-42; Neh 13:31; The efficacy of the priesthood and mediation of Christ is perpetual, and we can never approach to God in his name, by day or night, unseasonably. The ministers of Christ should have the fire of their zeal constantly burning. Leviticus 6:14”

“The fire of the altar was also to be kept burning "with it" (בּו, viz., the burnt-offering) the whole day through without going out. For this purpose the priest was to burn wood upon it (the altar-fire), and lay the burnt-offering in order upon it, and cause the fat portions of the peace-offerings to ascend in smoke, - that is to say, whenever peace-offerings were brought, for they were not prescribed for every day. Leviticus 6:13”