The father, Abner, is wearing his black coat for moving. He is leaving because the community accused him.
Abner is being accused of barn burning, which is a serious offense. His younger son, Sarty, is asked to testify against him at his trial.
His father, stiff in his black Sunday coat donned not for the trial but for the moving, did not even look at him. He aims for me to lie, he thought, again with that frantic grief and despair.
The case is dismissed, but Abner moves his family out of protest and derision for the community that would accuse him.
The coat is symbolic. It represents Abner’s intractable nature and his staunch proclamation of innocence. He is horrified that anyone would suspect him or accuse him. The “iron like black coat” is his haughty defense. He refuses to acknowledge his guilt.
The coat also demonstrates the son’s growing realization of what his father is. In the beginning, the coat is pristine. In the son’s eyes, his father can do no wrong. Sarty assumes the world is out to get his father, and it is all some mistake. Throughout the development of his understanding that his father really is a barn burner, the son begins to see the coat as a costume rather than sophistication. When he finally acknowledges what his father truly is, the coat is “at once formal and burlesque.” The son has come to understand the father for what he really is. Sarty sees Abner as a cartoon, and loses his faith in him. Turning on him does not even seem like a betrayal, because the father betrayed the son's trust long ago.