Scout says that she was used to listening to her father's elevated style of speaking, but many times she doesn't understand him. For example, when Atticus tells Scout the legal definition of rape is "carnal knowledge of a female by force and without consent," she responds by asking why Calpurnia wouldn't answer her if that is all it was. Clearly, Scout might be used to hearing her father talk with his legal jargon, but she doesn't understand it. Thus, when Atticus tells the children not to use their rifles on mockingbirds because it's a sin, she understands the words, but she doesn't understand the profound meaning behind them. Therefore, Miss Maudie expounds on the subject later when she and Scout are talking together. Miss Maudie says the following:
"Mockingbirds don't do one thing but make music for us to enjoy. They don't eat up people's gardens, don't nest in corncribs, they don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird" (90).
Miss Maudie gives Scout the literal and symbolic meaning behind Atticus's advice. Because Maudie is a good person and a trusted friend, Scout listens to her with great attention. Miss Maudie's clarification of what Atticus says helps to solidify the theme and title of the book. Scout understands this explanation a little bit better because Maudie gives her specific details behind the saying. Maudie's clarification is used later as Scout applies it to Boo Radley and Tom Robinson. Neither man did anything to hurt anyone else, but they were treated with disrespect and hatefulness.
In Chapter 10 of "To Kill a Mockingbird,"Mis Maudie tells the children,
Mockingbirds don't do one thing but make music for us to enjoy. They don't eat up people's gardens, don't nest in corncribs, they don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird.
Of course, this passage is significant in its symbolism. Tom Robinson, the mockingbird of the town, is kind and innocent. He does not bother anyone; he only helps the Ewell girl out of human charity. Thus, the sin that the Ewells and the townspeople commit is in their distorted perception that Tom has crossed a civil line. A man of his word and moral conscience, Atticus recognizes this sin and feels compelled to defend Tom because the moral rules supercede any man-made rule.