I heard a sketch somewhere or read a joke in a book or magazine. All I can remember is the punchline, which went something like this. A Jewish father has been having a discussion with his adult son and finally says: "Look, by you you are a lawyer. By Mama you are a lawyer. And by me you are a lawyer. But by a lawyer are you a lawyer?"

"lawyer" could have been "doctor", "dentist", "musician", whatever.

Does anyone know the full, correct story? Can you post it here?