The Master said, "When I walk along with two others, they may serve me as my teachers. I will select their good qualities and follow them, their bad qualities and avoid them."
子曰、三人行、必有我師焉、擇其善者而從之、其不善者而改之。
Analects 7.22
The same idea in other traditions
Contemplate and reflect upon knowledge, and you will become a benefactor to others.
Give instruction to a wise man, and he will be yet wiser: teach a just man, and he will increase in learning.
A man is not learned because he talks much; he who is patient, free from hatred and fear, he is called learned.
Therefore, seeker after the highest truth, study the sacred lore, in order to cause yourself and others to attain perfection.
The fear of the LORD is the beginning of wisdom; A good understanding have all they that do thereafter; His praise endureth for ever.
…Say: "Are those equal, those who know and those who do not know? It is those who are endued with understanding that receive admonition.
Little is known by any one but the spiritual man, / Who has in his heart a touchstone of vital truth. / The others, hovering between two opinions, / Fly towards their nest on a single wing. / Knowledge has two wings, opinion only one wing; / Opinion is weak and lopsided in its flight. …
After having taught the Veda, the teacher instructs the pupil: 'Say what is true! Do thy duty! Do not neglect the study of the Veda! After having brought to thy teacher his proper reward, do not cut off the line of children! Do not swerve from the truth! Do not swerve from duty! Do not neglect what is useful! Do not neglect greatness! Do not neglect the learning and teaching of the Veda!