Per a parenting book I read, I've taught Ezra that when Jude hits him or does something else hurtful, he should tell Jude that he doesn't like it. But often from the next room I hear:
Ezra: Jude, I don't like it when you hit me! OW! I don't like it when you hit me! Jude, I don't like it when you hit me! OW! I don't like it when you hit me, Jude! OW!
And Jude's just going whappity whappity whappity.