chá qí yǒu, zhī qí rén
察 其 友, 知 其 人

A man is known by the company he keeps.

解释 ( paraphrase )

This proverb tells us people of the same tastes and habits like to be together and influence each other. If one behaves well, his friends are also noble-minded. If a person behaves badly, his friends are not supposed to be honorable. Therefore, a man can be known by the company he keeps.
The proverb advises us to make good friends and right decision. A well-behaved friend can benefit you and an immoral friend will lead you to enjoyment and laziness.