You could always threaten him with a nice pair of ears to go with that tail of his.
8 seconds sound clip from the Harry Potter and the Sorcerer's Stone movie soundboard.
You can hear this line at 02:29:23 in the Blu-ray version of the movie.
Quote context
[...]
- Thought you were leaving without saying goodbye, did you?
- Go on. On with you. On with you now.
- Oh, listen, Harry. If that dolt of a cousin of yours, Dudley, gives you any grief...
- You could always threaten him with a nice pair of ears to go with that tail of his.
- But Hagrid, we're not allowed to do magic away from Hogwarts.
- I do. But your cousin don't, do he?
- Feels strange to be going home, doesn't it?
- I'm not going home. Not really.
[...]