Atticus is talking to Jem and Scout about Mrs. Dubose. Mrs. Dubose would always sit on her porch and comment as the children passed her house. One day she said,
"Your father's no better than the niggers and trash he works for" (pg 102)
Jem gets so upset with this that he takes Scout's baton and cuts all the tops off of Mrs. Dubose's camelia bushes. For this he was punished, He cleaned up the front yard and promised to work every Saturday on her yard to try to grow the camelias back to their original condition, and he had to read each day to Mrs. Dubose every afternoon and Saturdays for two hours. Later the reader finds out that Mrs. Dubose was a morphine addict.
"She took it as a pain killer for years. The doctor put her on it. She'd have spent the rest of her life on it and died without so much agony, but she was too contrary" (pg 111)
She wants to die free of the morphine addiction, and she succeeds. When she does die, she sends Jem a camelia in a box. At that time, Atticus explains,
"I wanted you to see what real courage is. Instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin, but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do. Mrs. Dubose won, all ninety-eight pounds of her. According to her views, she died beholden to nothing and nobody. She was the bravest person I know. " (pg 112)
These quotes are from my version of the book. They should be relatively close to these pages. They are all in chapter 11.
There are different version of the book, but it is at the end of chapter 11.