《管子·匡君小匡》
管子回答说： 士农工商四民，是国家的柱石之民，不可使他们杂居，杂居则说的话做的事都不一样。
管子对曰： 士农工商四民者，国之石民也，不可使杂处，杂处则其言哤，其事乱。
Guanzi replied: The four peoples, namely, scholars, peasants, workers and merchants, are the pillars of the state, and they should not be allowed to live in mixed communities, because their words and deeds are different in mixed communities.