Tang Taizong Li Shimin made great contributions at the founding of the Tang Dynasty, and the great cause of reunification was not yet completed, and major incidents occurred between the brothers. Li Jiancheng and Li Yuanji were jealous of Li Shimin's high merits and wanted to kill Li Shimin. After several failed attempts, Li Shimin, under the persuasion of Wei Chigong, Cheng Yaojin, and other subordinates, launched the Xuanwumen Rebellion, killed Li Jiancheng and Li Yuanji, and successfully ascended to the throne of the crown prince.
When Li Shimin became crown prince, all of his subordinates were promoted to higher ranks, and the ministers advised Li Shimin that Li Jiancheng and Li Yuanji's former ministers should also be reinstated to their respective positions to show the prince's virtue. Li Shimin felt justified and reinstated all of Li Jiancheng and Li Yuanji's subordinates.
Among Li Jiancheng's former ministers was Wei Zheng, who had been favored by Li Shimin, the King of Qin, but after returning to Tang, Wei Zheng had always served as Li Jiancheng's teacher, and Li Shimin did not reinstate Wei Zhengguan, but deliberately rebuked Wei Zheng, saying: "When you were in Dongfu, why did you alienate my brother, so that I was almost secretly calculated?" Wei Zheng listened to him and did not hesitate to scold him: "Obeying the emperor's orders for his subjects is a matter of course and righteousness, and the establishment of rebellion has nothing to do with being a taifu and has nothing to do with it." ”
Li Shimin originally did not really blame Wei Zheng, he just showed his majesty in front of Wei Zheng, seeing that Wei Zheng had no fear, he admired Wei Zheng even more, he immediately put down his face, nodded his head, and smiled at Wei Zheng to entrust Wei Zheng with a heavy responsibility, and worshiped Wei Zheng as the master of zhan affairs. After Li Shimin became emperor, Wei Zheng dared to speak directly, and Li Shimin was very afraid of him, but still had great respect for Wei Zheng, regarded Wei Zheng as a mirror of himself, often saw his words and deeds, and alerted himself to work hard. From this, it can be seen that if a person who is just and upright meets Ming Jun, his ending will be a comedy, otherwise it will be a tragedy.