唐朝人张在河阳县任县尉时，发生一位过路客因缰绳断了，连驴带鞍一起丢失的事。这个客人找了3天都没有着落，便到县府里投案告状。县尉张变对偷驴案追查得很紧，因此盗贼惶惶不安，连夜将驴子放走，但却私藏了鞍子。张见驴子回来了，便说：“就凭这点，便可得知是谁偷驴子了。 When the Tang dynasty was in Renyang County in Heyang County, a passing passenger was broken by the reins and even the donkey was lost with his saddle. The guest did not find the three days to find a place, they went to the county court surrendered. Lieutenant Zhang County on the steal donkey investigation is very tight, so the thieves panic, the donkey to let go overnight, but possession of the saddle. Zhang see the donkey back, then said: "With this point, we can know who stole the donkey.