From
韩愈《马说》 (Han Yu, Tang, ~800 CE), a short allegorical essay:
世有伯乐,然后有千里马。千里马常有,而伯乐不常有 (The world must first have a Bole, and then there can be a thousand-li horse. Thousand-li horses are common; a Bole is not).
伯乐 = the legendary Qin-era horse-judge; a classic meditation on talent going unrecognized.