A man of the state of Zheng (zhèng guó 郑国) wanted to buy a pair of shoes. He measured his foot and put the measurement on a chair. When he set out for the market he forgot to bring it along. It was after he had found the pair he wanted that this occurred to him.
"I forgot the measurement",said he.
He went home to get it but when he returned the market had broken up and he did not get his shoes after all.
"Why didn't you try on the shoes with your feet? "
He was asked " I 'd rather trust the measurement han trust myself."

从前，郑国有个人想买双鞋。他量好了自己脚的尺码，把它放在了椅子上。可当他赶往市集时，却忘了带量好的尺码。他要买鞋时，才想了起来。
他说：“我忘带尺码了。”
他回家去取量好的尺码。 等他赶回来时，市集已经关了，他还是没能买到鞋。
有人问：“为什么不用你自己的脚去量鞋子呢？”
他说：“我宁愿相信尺码也不相信我自己的脚。”

郑人买履 (zhèng rén mǎi lǚ)
【翻译】Buying shoes.
【释义】用来讽刺只信教条，不顾实际的人。
【例句】我们做事要根据实际的情况进行灵活调整，千万不能像郑人买履一样。
【近义词】生搬硬套、死搬教条
【反义词】看风使舵、见机行事