It is good to act selflessly toward others
Billy sees a ball fly over his fence and lands in his yard.
Billy wants to decide what to do with the ball.
Billy decides that the other person who lost this ball is more important than him having an extra and throws it back.
Billy takes a ball and keeps it for himself, since it landed in his yard.
"Billy hears someone call ""Thank you!"" as he sees the ball sail back other the fence."
Billy now has one more ball than he already has by claiming this one.