《韩非子·内储说上七术》
所以韩昭侯肯定知道南门外情况，然后其他三个门外面的情况也能搞清；周君要下令搜寻弯曲的手杖，引起群臣恐惧；卜皮要指派侍仆刺探御史，西门豹要假装丢失车辖。
故必审南门而三乡得。周主索曲杖而群臣惧，卜皮使庶子，西门豹详遗辖。
So Han Zhaohou must have known the situation outside the South Gate, and then the situation outside the other three gates could also be clarified; King Zhou wanted to order a search for the crooked staff, which caused fear among the courtiers; Bupi wanted to assign servants to spy on the Censor, Ximen Bao wanted to pretend to lose the car axis.