- To kill Caesar! Does Commodus know?
- Commodus does not know. He must never know.

9 seconds sound clip from the The Fall of the Roman Empire (1964) movie soundboard.

You can hear this line at 00:58:15.642 in the Blu-ray version of the movie.

Quote context

[...]

- What would you like? That the gods send us written messages advising us on each small move we make?

- Is the murder of an emperor a small move?

- Murder?

- Caesar is dying and knows it.

- At any moment, he will disinherit Commodus and proclaim Livius his heir.

- Once he does that, publicly, what hope is there for us?

- To kill Caesar! Does Commodus know?

- Commodus does not know. He must never know.

- Caesar is guarded. There are so many close to him.

- How can it be done?

- Quite easily.

- We all of us know that Caesar loves fruit. Apples.

- Now, this blade carries a deadly poison, on the side with the carved snake. Cut fruit with it, an apple. Offer the poisoned half to Caesar. Eat the other half for yourself...

[...]