Pardon me, sir, you don't understand.
5 seconds sound clip from the A Chump at Oxford (1939) movie soundboard.
You can hear this line at 00:48:50 in the DVD version of the movie.
Quote context
[...]
- I know it. I was never so sure in my life.
- Well, I've known him for years and he's the dumbest guy I ever saw.
- I certainly am. That's why I'm here.
- Pardon me, sir, you don't understand.
- I can recall your accident most vividly.
- It happened in this very room. It was right here, at this very window.
[...]