Make Your Child Understand The Concept of 'Karma'
It is important for your child to understand that we reap what we have sown. In other words, what you give is what you get. You can demonstrate this simply by pretending to hit your fist against the wall and act hurt. You can then say that I hit the wall, so it hit me back and see, it is hurting now.
This way he will understand that in life, what you give others is what you get back. And that is why we need to be careful about our actions. Since if we give pain to someone, we will get that pain back, and if we give happiness to someone, we will get that happiness back.