They got the carving knife to cut the pussycat's life. The puss will get the knife for trifling with three blind mice.
12 seconds sound clip from the Dr. No movie soundboard.
You can hear this line at 00:03:02 in the Blu-ray version of the movie.
Quote context
[...]
- That's it! Hundred honors and ninety below.
- Nicely done, Strangways. I have to give it to you.
- Afraid I must leave you for a few minutes.
- Order a round on my chit, will you, Professor?
- Right.
- Damn it all! Must you break off at this time every evening?
[...]