Zen students are with their masters at least ten years before they presume to teach others. Nan-in was visited by Tenno, who, having passed his apprenticeship, had become a teacher. The day happened to be rainy, so Tenno wore wooden clogs and carried an umbrella. After greeting him Nan-in remarked: “I suppose you left your wodden clogs in the vestibule. I want to know if your umbrella is on the right or left side of the clogs.”
Tenno, confused, had no instant answer. He realized that he was unable to carry his Zen every minute. He became Nan-in’s pupil, and he studied six more years to accomplish his every-minute Zen.
( found at ashidakim.com )