刀不磨要生銹，人不學要落後 [－－－－－锈－－－学－－后]

Jyutping
Pinyin dāo bù mó yào shēng xiù , rén bù xué yào luò hòu

Definitions (CC-CEDICT)
  1. a blade will get rusty if it is not sharpened; a man will fall behind if he doesn't study (idiom)