Fire is an important symbol in "Barn Burning," as you might expect. We talk about fire in almost every section of this guide. Here we want to focus on the fire Abner builds the night the family camps out before arriving at the de Spain place.
The narrator describes the fire Abner builds that night, and the fires he always builds when camping, as "neat, niggard almost, shrewd" (27). We want to make a note here that "niggard" means "stingy." "Shrewd," in this case, probably means that the fire was built to burn as long as possible on as little wood as possible. This is an odd moment because the narrator tells us that if Sarty were older, he might have wondered why his father built small campfires. We then hear about the different conclusions Sarty might have come to, again, if he were older. Finally, the narrator reveals the "true reason" for the small fires:
[T]he element of fire spoke to the mainspring of his father's being […] as the one weapon for the preservation of integrity […], and hence to be regarded with respect and used with discretion. (127)
This suggests strongly that without fire, Abner would feel completely powerless and out of control. Fire is the one thing in his life he can control. From the small fires made at camp to the larger ones that burn down barns, Abner is the boss. This is interesting when taken with the phrase "without heat" used to describe the way Abner hits his mules, and his son (21, 29). This seems like another way of saying that Abner doesn't hit out of anger, or strong, burning emotion. Rather, his hitting is as calculated as his fire burning – he does it for a reason, to make the person or animal he hits do what he wants. Ironically, fire and hitting, the things that give Abner control over his life, render those around him powerless.