There are many magic rings in this world, and none of them should be used lightly.
7 seconds sound clip from the The Lord of the Rings: The Fellowship of the Ring movie soundboard.
You can hear this line at 00:26:06 in the Blu-ray version of the movie.
Quote context
[...]
- I, uh... I have things to do.
- I've put this off far too long.
- I regret to announce this is the end! I'm going now. I bid you all a very fond farewell. Goodbye.
- I suppose you think that was terribly clever.
- Come on, Gandalf. Did you see their faces?
- There are many magic rings in this world, and none of them should be used lightly.
- Oh, you're probably right, as usual.
- You will keep an eye on Frodo, won't you?
- Two eyes. As often as I can spare them.
- I'm leaving everything to him.
- What about this ring of yours? Is that staying too?
[...]