Zen Master Nansen's "What the Holy Ones Have Not Preached"

The Case

Zen master Nansen came to see Hyakujo. Hyakujo said, "Is there any Law that the holy ones have not preached to the people?" Nansen said, "There is." Hyakujo said, "What is the Law that has not been preached to the people?" Nansen said, "It is not mind, it is not Buddha, it is not things." Hyakujo said, "You have preached." Nansen, "I am like this. How about you?" Jo said, "I am not a man of great Wisdom. How can I tell if there is preaching or no preaching?" Nansen said, "I don't follow you." Jo said, "I have talked quite enough for you."

Verse

Patriarchs and Buddhas have not preached,
Yet monks run after preachers.
Clear mirror on the stand, sharply imaging.
Looking southward, see the Great Bear.
The shaft hangs down. Where do you find it?
Saving your nostrils, you have lost your mouth.