I assume that you are looking for quotes that show that people in Maycomb during the time the book was set were prejudiced -- not that you are looking for evidence that Harper Lee herself was prejudiced. If that is the case, there are some examples.
Here are a couple of them:
The sheriff hadn't the heart to put him in jail alongside Negroes, so Boo was
locked in the courthouse basement.
That shows that people did not think that it was right to put a white suspect in with black suspects.
Then, in Chapter 6, we find that Mr. Radley has shot at a "Negro" just for being in his collard patch. Miss Stephanie says Mr. Radley missed:
Shot in the air. Scared him pale,
though. Says if anybody sees a white nigger around, that's the one.
Another less obvious example of prejudice in To Kill a Mockingbird comes when Miss Caroline proudly announces that "I am from North Alabama, from Winston County."
The class murmered apprehensively, should she prove to harbor her share of the peculiarities indigenous to that region.
Scout goes on to reveal the reasons for the first graders' concern. Winston County had seceded from Alabama following the state's secession from the Union prior to the Civil War. North Alabama was an area of ne'er-do-wells:
... full of Liquor Interests, Big Mules, steel companies, Republicans, professors, and other persons of no background.