What is the metaphor of bosom friend in traditional culture?

"Mountain Flowing Water" originated from Liezi? Tang Wen, it is said that Boya is good at drumming and Zhong Ziqi is good at listening. Boyasso

Look, Zhong Ziqi will win. Boya's ambition is to play the piano in the mountains. Zhong Ziqi said, "It is good to play the piano, but it is magnificent if you are on Mount Tai.". But his ambition is to play the piano in running water. Zhong Ziqi said, "Well played, like a river." Zhong Ziqi died, Boya broke the piano and never played it again, thinking that there were not enough pianos in the world. Later, I used "high mountains and flowing water" as a metaphor for a bosom friend or confidant.