chapter 9-10

Do you mean any line?

Atticus said to Jem one day, 'I'd rather you shot at tin cans in the back yard, but I know you'll go after birds. Shoot all the blue jays you want, if you can hit 'em, but remember it's a sin to kill a mockingbird.'"That was the only time I ever heard Atticus say it was a sin to do something, ch 10

This speaks to the central theme of the book. Hurting living things that just want to be good is a sin. Boo functions as a misunderstood person who is actually the opposite of what people perceive him to be. Like Tom Robinson, Boo Radley functions as a mockingbird-figure. He is mentally fragile and wants to do good for others.