All you do is put it opposite the magician's mirror, and it will explode within one hour.
10 seconds sound clip from the Return Of The Kung Fu Dragon movie soundboard.
You can hear this line at 00:50:00 in the Blu-ray version of the movie.
Quote context
[...]
- I have come to destroy the magician's mirror.
- His mirror? We can steal it.
- We can't. It's too heavy. We can destroy it with this.
- All you do is put it opposite the magician's mirror, and it will explode within one hour.
- You said the princess had disguised herself as a black girl. But then where is she?
- What's wrong? I think there's something wrong. Be careful.
- We must get to that mirror. Please let me do it. You won't regret it.
[...]