ㄇㄛˊㄔㄨˇㄔㄥˊㄓㄣmóchǔ‑chéngzhēn

磨杵成针
  1. 輿勝覽記載求學途中見老婦人鐵杵磨成針深受感動於是發憤向學比喻只要持之以恆努力困難完成 磨杵成針精神成事必備條件」。

to grind an iron bar down to a fine needle (idiom)​; fig. to persevere in a difficult task, to study diligently