From the Genjō kōan

"At the end of his Genjōkōan, Dōgen cites a dialogue between a monk and Master Pao-ch’e of Mt. Ma-ku.

As Pao-ch’e was fanning himself, a monk came by and asked, 'The wind’s nature is eternal and omnipresent. Why, reverend sir, are you still fanning yourself?'
The master replied: 'You only know that the wind’s nature is eternal, but you do not know the reason why it exists everywhere.'
The monk asked, 'Why does it exist everywhere?'

The master just fanned himself."

Translated in Francis H. Cook, Sounds of Valley Streams: Enlightenment in Dōgen’s Zen – Translation of Nine Essays from Shōbōgenzō. Albany: State University of New York Press, 1989.p. 69.

Cited by Miraldo in Journal of Buddhist Ethics, vol 13, 2006