《史记·七十列传·酷吏列传》
一年以后，关东郡国的官吏察看郡国中出入关口的人，都扬言说： 宁肯看到幼崽哺乳的母虎，也不要遇到宁成发怒。 
岁馀，关东吏隶郡国出入关者，号曰 宁见乳虎，无值宁成之怒 。
A year later, officials in the Guandong county checked the people entering and leaving the pass in the county, and all said: "I would rather see a tigress nursing the cubs than meet Ning Cheng's anger."