Then bathe them in medicinal water. This will toughen their skins. And it builds up their resistance to heat and to cold. Also, to external force, thus preventing serious injury.
18 seconds sound clip from the Shaolin Chastity Kung Fu movie soundboard.
You can hear this line at 00:33:50.341 in the DVD version of the movie.
Quote context
[...]
- You'll have to push them and guide them.
- Teacher, some of them are still so very young. If I push them, I'm afraid...
- It's for their own good. We have no time. We must go and train them hard.
- And then rub their bodies to stimulate the circulation.
- I'm fine, come on. Let's continue.
- This will turn your muscles really hard.
[...]