What is the seven-character legend left behind in the story of Boya Guqin?

The story "Bo Ya Gu Qin" leaves behind a seven-character legend: Meeting a bosom friend in high mountains and flowing water. "Bo Ya Gu Qin" is a story that happened to Boya on his way to visit his relatives. Among the ancient books, "Lu's Spring and Autumn Annals" contains folk stories about Boya Juexian, which established the noble standards of interpersonal relationships and friendship of the Chinese nation.

Bo Ya, a senior official of the Jin State during the Spring and Autumn Period and the Warring States Period, was originally from Yingdu, Chu State (today's Jingzhou, Hubei Province). Boya was a famous luther player at that time. He was good at playing the lyre and had superb skills. He is both an expert piano player and a composer, and is respected as the "Piano Immortal". "Xunzi: Encouraging Learning" once said that "Bo Ya played the harp while the six horses raised their heads", which shows his superb playing skills.