הלכה על יומא 42:5

The commandment of lighting fire on the altar every day: To burn (some have the textual variant, to have) fire on the altar every day perpetually, as it is stated (Leviticus 6:6), "A perpetual fire shall burn on the altar." And the explanation of perpetual came [that] it means to say to place wood in the morning and in the afternoon. And in the elucidation, they, may their memory be blessed, said (Yoma 21b), “Even though the fire descends from the Heavens, it is a commandment to bring [it also] from the commoners. And do not let it be difficult for you, to say, "What is this commandment – is it not that they, in any case, had to burn a fire for the sake of the sacrifice that they were obligated to bring, as it is impossible [to do so] without fire." As this is a commandment on its own; since besides the fire for the sacrifice, they would place fire on the altar for this commandment – and as they, may their memory be blessed, expounded (Yoma 45a), there were three arrangements of fire [derived] from the verses, as we will write in the laws of this commandment.