Dongshan's No Grass (BS89)

KOAN:

Dongshan instructed the assembly and said, “At the beginning of autumn and the end of summer, you, brothers, are departing east and west. Thus you go directly to the place of no grass over ten thousand miles.” And again he said, “How will you go to the place of no grass over ten thousand miles?”
A few weeks later, Shishuang said, “When you go out of the gate, there is grass all over!”
Over a century later, Dayang said, “I would say: Even if you don’t go out of the gate, grass is abundant everywhere.”