The Red Pony
How we cite our quotes:
Jody felt very sad. "If you'd like a glass of lemonade I could make it for you."
Grandfather was about to refuse and then he saw Jody's face. "Yes, it would be nice to drink a lemonade."
Jody ran into the kitchen where his mother was wiping the last of the breakfast dishes. "Can I have a lemon to make a lemonade for Grandfather?" (4.164-4.166)
At the end of the book, Jody does his Grandfather a solid. In a way, he's fulfilling a grandkid's duty to his Grandpa—getting the poor old guy a nice lemonade, but it's also an important step into adulthood. So in a weird way, he's fulfilling his duty to himself, too.