A man of honest and straightforward character, who admired Fu Zi's reputation but had never met him, arranged an introduction through a mutual friend and went to visit Fu Zi.
Fu Zi, dressed in a loose robe with wide sleeves, received his guest with solemnity. The guest thought to himself, "Fu Zi is very famous and learned; I should be sincere with him." He happily conversed with Fu Zi, openly sharing his views on various matters. Unexpectedly, before long, Fu Zi appeared displeased.
The friend who made the introduction asked Fuzi, "Did we do something wrong? Please advise us, sir."
Fu Zi said arrogantly, "Your guest has three faults. Laughing at me shows frivolity; asking for advice without addressing me as teacher is improper etiquette; speaking candidly on a first meeting is out of order."
A guest strongly disagreed with Fuzi's remarks and countered, "You are mistaken. Smiling at someone is a gesture of goodwill; asking for advice without calling them 'teacher' is because 'teacher' is just a common title, not necessarily reserved for instructors; and speaking deeply despite a shallow acquaintance is a sign of sincerity! When Emperor Yao once met Shun in a grassy field, they sat together under a mulberry tree on a ridge, talking freely for a long time until the sun's shadow shifted between two trees, and Yao ultimately ceded the empire to Shun. If deep conversation were forbidden with a shallow acquaintance, then the empire would never have been passed on!"
Later, the idiom "Jiao Qian Yan Shen" came to be used, meaning to speak one's heart to someone with whom one has only a shallow acquaintance.
Source: *Strategies of the Warring States*, Chapter "Strategies of Zhao IV"
Meaning of the Idiom: Later, the Chinese idiom "交浅言深" came to describe how to speak one's heart to someone with whom one has only a shallow acquaintance.