This is serious.

4 seconds sound clip from the Five Fingers of Death movie soundboard.

You can hear this line at 00:38:54 in the DVD version of the movie.

Quote context

[...]

- And now remember this. The Iron Fist technique can be lethal. Only use it in the course of justice. Do not ever use it for your own glory in private matches or quarrels.

- No sir. I shan't forget.

- Dad.

- What's this? Learning the Iron Fist technique?

- You know what a terrible weapon that is. If he does learn the secret art...

- This is serious.

- If Chao Chih-Hao wins the tournament, even if we manage to get Sun Hsin-Pei, we won't be any better off than we are now.

- That's enough!

- Don't give up. We professional fighters stick by each other. You get out.

- Okada, the karate expert. He'll be arriving here from Japan with two friends.

[...]