玉不琢,不成器 [－－－－－－－]

Jyutping juk6 bat1 doek3 , bat1 sing4 hei3
Pinyin yù bù zhuó , bù chéng qì

Definitions (CC-CANTO)
  1. a piece of jade without chiselling will not become a useful vessel; the finest diamond must be cut