When Bob Ewell spits in his face, Atticus only wipes it off.
Bob Ewell is very angry when Atticus defends Tom Robinson, but he is even angrier with the outcome of the case. Although Tom is not acquitted, it is clear that he is convicted only because he is a black man who was hanging around a white woman. Every man on that jury, and every person in town, knows that he didn’t do it. This infuriates Bob Ewell, who feels humiliated. This is the reason he spits in Atticus’s face. The fact that the jury deliberated for as long as they did proved that Atticus had a case, and they actually thought about letting Tom go. Bob Ewell cannot live with that shame.
Scout hears from Miss Stephanie Crawford that Bob Ewell cursed Atticus and threatened to kill him, and then spit in his face.
Miss Stephanie said Atticus didn't bat an eye, just took out his handkerchief and wiped his face and stood there and let Mr. Ewell call him names wild horses could not bring her to repeat. (Ch. 23)
Bob Ewell asked Atticus if he was too proud to fight, and he responded that he was too old. He told his children that he was just relieved that Bob Ewell did not chew tobacco. Scout is worried about her father’s safety, and wonders if he shouldn’t carry a gun. Jem reminds her that he never would.
The incident foreshadows Ewell’s attack on the Finch children later in the book. Bob Ewell is an angry, violent man. When he attacks the Finch children he is drunk. He is clearly abusive toward Mayella for one thing. He is the one who hit her, and hit her regularly. Atticus proved it, and made sure the whole town knew it.