Bob Ewell's confrontation with Atticus takes place in Chapter 23 of To Kill a Mockingbird. It was Miss Stephanie Crawford who witnessed the threats made by Bob, and she is quick to spread the word around town. Atticus would say little about it, but according to Miss Stephanie,
Atticus was leaving the post office when Bob Ewell approached him, cursed him, spat on him, and threatened to kill him.
Atticus "didn't bat an eye," and merely retrieved his handkerchief to wipe the spit out of his face. Ewell continued to curse Atticus, but Atticus' peaceful lack of retaliation only angered him further.
"Too proud to fight, you nigger-lovin' bastard?" Miss Stephanie said Atticus said, "No, too old."
Atticus then nonchalantly walked away. His only response was that
"I wish Bob Ewell wouldn't chew tobacco."
Atticus' actions are really no surprise. He discourages Scout to fight and refuses to tell his children about his marksmanship abilities. He is a peaceful man whose actions always speak louder than words.