According to the late Dr. Joan McCord, Criminologist

Let’s consider the child that is hitting his sibling. You’d like him to stop. You can:

1) hold his hands and say, “stop hitting. Do you see how you’re hurting your brother?”
2) say “Stop hitting or I’ll punish you.”
3) say “Stop hitting,” and then hit the child.

Let’s have a look at each of these actions and the results:

1) The child is taught that hitting the brother is a wrong thing to do. It’s a reason for not hitting.

2) It’s implying that “I,” the person who’s gonna hit, have the power and can hurt you. The child has to figure out whether it’s because you’re a parent, because you’re bigger, what are the circumstances that you have a right to give pain, and you’ve introduced the whole notion of giving pain.

3) If you hit the child, the child’s problem is then to figure out when it’s alright to hit, and he’ll start hitting more.

There’s lots and lots of evidence that shows that children who are hit are more likely to be hitting later on, and it’s even a very good predictor of crime later on.