Early in the narrative of To Kill a Mockingbird, Miss Maudie tells the children, "Atticus Finch is the same in his house as he is on the public streets." This observation of Miss Maudie indicates that Atticus believes in the power of example. Therefore, he is aware of his own behavior constantly so that his children will observe his example and learn from it.
Applying this concept to the incident of Jem's vindictive cutting of Mrs. Dubose's camellias, Atticus decides that his son will better learn what kind of person Mrs. Dubose really is by observing how she conducts herself, and not by her drug-induced words. Therefore, he assigns Jem the task of reading to her each day for a designated time. Finally, the sentence is completed and Jem is no longer required to visit her and read.
Then, one day Atticus returns home with a shoe box containing a perfect white camellia; Jem is annoyed that she will not "leave [him]alone"; however, his father disabuses him of this idea as he explains that Mrs. Dubose had actually been withdrawing from morphine addiction and enduring tremendous pain while Jem read. Atticus tells his son,
"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."
From Mrs. Dubose, Jem learns a lesson that his father will later underscore at the Tom Robinson trial: The noble fight against their foes even when they know they will be beaten because doing so is the morally correct thing to do.