Be careful, both of you. The enemy has many spies in his service: Birds, beasts.
— Gandalf (Ian Mckellen)
10 seconds sound clip from the The Lord of the Rings: The Fellowship of the Ring movie soundboard.
You can hear this line at 00:43:14 in the Blu-ray version of the movie.
Quote context
[...]
- Please, Mr. Gandalf, sir, don't hurt me. Don't turn me into anything unnatural.
- I've thought of a better use for you.
- Come along, Samwise. Keep up.
- Be careful, both of you. The enemy has many spies in his service: Birds, beasts.
- Never put it on for the agents of the Dark Lord will be drawn to its power.
- Always remember, Frodo... the Ring is trying to get back to its master. It wants to be found.
[...]