不耻下问 bùchǐ-xiàwèn
[do not feel ashamed to ask and learn from the rank and file;be modest enough to consult one's inferiors] 不把向学问、地位等不如自己的人请教当成可耻的事。形容谦虚、好学
敏而好学,不耻下问。——《论语·公冶长》