The man referred to by the father in line 17 of "Barn Burning" appears to be connected to the contentious construction of a new barn, a matter causing familial strife.
From the various excerpts provided it seems clear that the man referred to by the father in line 17 of "Barn Burning" is likely involved with the construction of a new barn, which is causing some distress within the family.
The man's identity is not clarified in these excerpts, but the context suggests that he is likely a worker or someone involved in the agricultural business, as the new barn and the addition of cows seem to be significant points of discussion.
The story "Barn Burning" seems to explore themes of family, obligation, and the moral struggles that can divide households. The tension surrounding the new barn and the unnamed man's role highlights a conflict between characters, which is a critical aspect in understanding the story's dynamics and the characters' motivations.