During an evening talk, Dogen once said,

"When my late master Nyojo was the abbot of Tendo Monastery, while the monks were sitting zazen in the sodo (monks hall), he slapped them with his slipper or scolded them with harsh words in order to keep them awake. Yet each of them was thankful to be hit and highly respected him.

"Once in a formal speech he said, 'I have gotten old. I should have retired from the monastery and moved into a hermitage to care for myself in my old age. Nevertheless, I am the abbot and your teacher, whose duty is to break the delusions of each one of you and to transmit the Way; therefore, I sometimes use harsh language to scold you, or beat you with the bamboo stick. I regret having to do this. However, this is the way to enable the dharma to flourish in place of the Buddha. Brothers, please have compassion on me and forgive me for my deeds.'

"Upon hearing these words, all of us shed tears. Only with such a spirit can you teach and propagate the dharma."

(from Shobogenzo Zuimonki, Book 1, Chapter 7)