What are some quotations (with page numbers) about why Atticus should take the Tom Robinson case in To Kill a Mockingbird?

Atticus Finch feels that he must accept the position of defense attorney in the Tom Robinson case because it is both the moral and ethical thing for him to do.
Here are quotations that substantiate Atticus's beliefs:

1.  "Atticus Finch is the same in his house as he is on the public streets" (Ch.5, p. 50, Warner Books, paperback). 

This statement of Miss Maudie indicates that Atticus is a genuine person who truly practices the ethics he is sworn to uphold as a lawyer. Because he believes in doing what is right, he should be the attorney for Tom Robinson; moreover,  Tom's socio-economic level will be irrelevant to Atticus in his conscientious defense.

2. "But do you think I could face my children otherwise?" (Ch. 9, p.93). Atticus asks this question of his brother Jack, who has inquired if Atticus cannot avoid taking the case for Tom Robinson. Atticus's rhetorical question implies that if he does not defend Tom, then he is a hypocrite, and will not be able to look at his children without knowing that he lacks integrity and his children will realize this, as well. 

3. "If your father's anything, he's civilized in his heart" (Ch.10, p. 102). This statement simply elaborates on Miss Maudie's one from Chapter 5: Atticus is above pettiness and bias. He recognizes the "greater good" that should be followed, and, therefore, must defend Tom based upon moral principles.

4. "It's a sin to kill a mockingbird" (Ch. 10, p.94). This statement of Atticus implies that he recognizes the lack of malice that characterizes the mockingbird or any other innocent creature, be it bird or Tom Robinson.  As a simple man, Tom is innocent of any crime. He possesses Christian values, one of which is charity toward all persons. He has helped Mayella for no other reason than the fact that she has needed assistance with her chores.Therefore, for Atticus, it will be "a sin" of hypocrisy to not defend the mockingbird, Tom Robinson.

5.  "This case, Tom Robinson's case, is something that goes to the essence of a man's conscience--Scout, I couldn't go to church and worship God if I didn't try to help that man" (Ch.11, p.109).
This statement of Atticus indicates that he believes it is his moral duty to defend Tom Robinson. For, Atticus knows that Tom has done no wrong, and it is only the false accusations of the Ewells that have generated a trial. Atticus also realizes that the Ewells are making Tom their scapegoat for Mayella's forbidden behavior of kissing a black man.

6. "I wanted you to see what real courage is....It's knowing you're licked before you begin, but you begin, anyway, and you see it through no matter what" (Ch.11, p. 116). After telling this to his children, Atticus must take the Tom Robinson case or he will demonstrate that he lacks such courage. In other words, he must "practice what he preaches."

7. "Do you really think so?" (Ch.15, p.148). Atticus asks Link Deas this signature question of his after Link tells Atticus that he should not take the Tom Robinson case because he has "everything to lose...from this." However, Atticus knows that he will lose his integrity if he does not take the case; consequently, he asks Link Deas this rhetorical question to provoke Link's logic.