Symbolism, Imagery, Allegory
On the day of his wedding to Molly, Lucas Beauchamp lights a fire in their house's hearth. This fire has kept burning for the forty-five years they have been married. The fire symbolizes the endurance of their marriage; both are things that need to be attended to and fed to stay alive.
When Molly leaves Lucas for six months with their newborn son to nurse Zack Edmonds's motherless newborn son, Lucas has to work to keep the fire going:
"[...] his own wife, the black woman, keeping his baby in the white man's house and he now living alone in the house which old Cass had built for them when they married, keeping alive on the hearth the fire he had lit there on their wedding day and which had burned ever since though there was little enough cooking down on it now [...]." (2.1.2.11)
Mollie eventually returns and cooks on the fire like she used to. So we know that despite the difficulties they had during these months, Lucas still remained a faithful and dedicated husband, and she came back home with the same dedication to their marriage.
In "Pantaloon in Black," when Rider marries Mannie, he also builds a fire in his hearth, like Uncle Lucas had done forty-five years before. When Mannie dies, the day of her funeral is also the day the fire dies out in their hearth. When Rider goes home, he finds that the last meal she cooked has gone cold. The fire has died with Mannie, and Rider is left with a cold emptiness.
So, married folks, take our word of wisdom and don't let that fire die out.