You'd keep your mouth shut if you knew what was good for you, buddy.
4 seconds sound clip from the Dumb and Dumber movie soundboard.
You can hear this line at 00:29:31.469 in the Blu-ray version of the movie.
Quote context
[...]
- No. Oh no, sir. No no no. No, huh-uh.
- Come on, give me that booze, you little pumpkin-pie-haircutted freak! Come on!
- Sir, no, I-I... No, sir, don't. Don't drink...
- You'd keep your mouth shut if you knew what was good for you, buddy.
- Oh, it makes perfect sense, Mary.
- We should have called the authorities the minute we knew that Bobby was kidnapped.
[...]