A Perpetual Fire
This section is basically a review of the various offerings, albeit with many interesting additional bits of information. One fascinating fact we find in this passage is that the fire upon the altar was to be kept burning (Leviticus 6:9 Leviticus 6:9Command Aaron and his sons, saying, This is the law of the burnt offering: It is the burnt offering, because of the burning on the altar all night to the morning, and the fire of the altar shall be burning in it.
American King James Version×, 12-13). The Nelson Study Bible comments: "The fire on the altar was never to go out. This was accomplished at night with a burnt offering that was not extinguished. It could have been stoked with wood through the night to keep it burning. After being renewed in the morning [with wood] (see v. 12), the fire was kept going throughout the day for the succession of [various offerings].... Five times in this paragraph the priests are instructed to keep the fire burning. There are at least three reasons for this: (1) The original fire on the altar came from God (9:24). (2) Perpetual fire symbolized the perpetual worship of God. (3) Perpetual fire symbolized the continual need for atonement and reconciliation with God, which was the purpose of the offerings" (notes on 6:9 and verses 12-13).
When the altar was transported, the ashes were removed and a cloth was put on top (Numbers 4:13-14 Numbers 4:13-14  And they shall take away the ashes from the altar, and spread a purple cloth thereon:
 And they shall put on it all the vessels thereof, with which they minister about it, even the censers, the meat hooks, and the shovels, and the basins, all the vessels of the altar; and they shall spread on it a covering of badgers' skins, and put to the staves of it.
American King James Version×). The Jamieson, Fausset and Brown Commentary states in its note on verse 13: "No mention is made of the sacred fire; but as, by divine command, it was to be kept constantly burning, it must have been transferred to some pan or brazier under the covering, and borne by the appropriate carriers." Though we can't be certain about this, it is plausible since sacrifices were offered every morning and evening, which may well imply that they were done even at times of transport. When tabernacle worship was later transferred to the temple at the time of Solomon, God ignited that fire too. However, it is not known whether the same fire was kept burning through periods of apostasy when temple worship was abandoned, although it certainly could have been. However, there is no indication that God ignited the fire of the altar built after Judah's Babylonian captivity.