他山之石可以攻玉
tā​shān​zhī​shí​kě​yǐ​gōng​yù

external wisdom

他山之石可以攻玉 tā​shān​zhī​shí​kě​yǐ​gōng​yù
external wisdom
To utilize foreign expertise, talent, or the successful experiences of others to effectively develop a project or nation.
self-improvement
To improve one's own character or work by accepting and applying criticism or advice from outside sources.

Sources
Definitions
CC-CEDICT