打鐵還需自身硬 [－铁还－－－－]

Jyutping daa2 tit3 waan4 seoi1 zi6 san1 ngaang6
Pinyin dǎ tiě hái xū zì shēn yìng

Definitions (Wiktionary)
  1. phrase, idiomatic
    it takes a good blacksmith to forge good tools; to do a job well, one must be highly competent
    (syn.) 打铁先得本身硬, 打鐵先得本身硬