First of all, we must make it clear that this order was not given to Chai Jin, nor was it given by the "emperor of the dynasty". You may be too unfamiliar with this history.
No, no, no, I am not saying that Chai Jin's "Danshu Iron Coupon" is historical truth. I have not found any record of Chai Jin as a person in the historical records, he may have been just a literary figure. However, the setting of the character of Chai Jin in "Water Margin" is based on historical reality.
In "Water Margin", Xiao Er introduced: "He is a descendant of The Great Zhou Chai Shizong. Since Chen Qiao abdicated the throne, Emperor Taizu Wude gave him an oath iron coupon at home."
As soon as I said "Chen Qiao gave way", I remembered it, right? Zhao Kuangyin, Chen Qiao, mutinied, pulled a "concession" as a fig leaf, and also treated the descendants of the Later Zhou Chai family more gently. Originally, Zhao Kuangyin did not indiscriminately kill heroes like Zhu Yuanzhang to eliminate hidden dangers, but instead adopted the method of "power and wine to release military power" to relieve the power of military generals. This is true for military generals, and for the orphans and widows of the Chai family, there is no need to take extreme measures.
Therefore, under a special political protection, the descendants of the Chai family can continue the bloodline, breed heirs, and have some privileges at the local level. This is the origin of the "oath iron coupon" in "Water Margin".
In other words, the "iron coupon for the oath" in the "Water Margin" was issued by Taizu Zhao Kuangyin to Chai Rong's younger son, the last emperor of the Later Zhou Dynasty, and Chai Zongxun, who ascended the throne at the age of seven and abdicated at the age of eight, and then passed from father to son and son to grandson, and passed on to Chai Jin from generation to generation, rather than directly issued to Chai Jin by the emperor of the dynasty.
This "iron oath ticket" may have had some effect in the beginning. But in the hands of Chai Jin more than two hundred years later, it is only an honorary title, which is not much more valuable than Ah Q's "I was much broader before". Otherwise, we would not be able to explain how a brother-in-law of a prefect dared to forcibly occupy Chai Jin's uncle's garden water pavilion and drive Chai Huangcheng out of his house.
Chai Jin fell in Gaotang Prefecture, it was the good han of Liangshan who rescued him; after going to Liangshan and then surrendering to the Song Dynasty, it was the collective behavior of the Liangshan clique, and the emperor would not hold him alone; being a horse for breaking Fang La may also become a crime for Chai Jin, fortunately, this time he was sober-minded and quick-witted, and he resigned from the official in time and returned the official.
A commoner, without the influence and appeal of Song Jiang, would not pose a threat to the imperial court. This is the real reason why Chai Jin was able to not die, and it was much better than any "oath iron coupon"!