Li Guang, a famous Han Dynasty general, was exceptionally skilled in martial arts. His archery was particularly superb—he could hit a willow leaf from a hundred paces away, never missing his target. He guarded the northern border for years, and the Xiongnu, terrified at the mere mention of his name, dared not invade south, calling him the "Flying General." Hence, a Tang poem says, "If only the Flying General of Dragon City were here, no barbarian horsemen would dare cross the Yin Mountains."
According to legend, the famed Han Dynasty general Li Guang was once hunting at the southern foot of Mount Ming with a few attendants when he suddenly spotted a tiger lurking in the grass nearby. Swiftly, he drew his bow, nocked an arrow, and with all his strength, shot straight at the beast. Yet, the tiger remained utterly motionless.
After waiting a while, General Li Guang noticed the tiger remained utterly still, which struck him as odd. Cautiously approaching, he discovered it wasn't a tiger at all but a large rock shaped like one. Looking closer, he saw that both the arrowhead and the fletching had embedded themselves deep into the stone.
Li Guang could hardly believe his own strength. He retreated to where he had first shot, drew his bow with all his might, and fired at the rock again. Yet arrow after arrow failed to penetrate—some shattered on impact, others snapped in midair. Puzzled, he examined the stone up close, then turned to his men and said, "I cannot fathom this mystery." With that, he led his retinue back, leaving the riddle unsolved.
After many years, people found such actions hard to understand, so they went to seek advice from the scholar Yang Xiong. Yang Xiong replied:
"Sincerity can crack metal and stone." This means: with genuine sincerity, even hard objects like metal or stone can be opened. Later, the idiom "cracking metal and stone" came to describe how sincerity can move all things or touch others deeply.
Source: Ge Hong (Jin Dynasty), *Miscellaneous Records of the Western Capital*
Meaning of the Idiom: Later, the Chinese idiom "金石为开" came to describe how sincerity can move all things or touch others deeply.