"Three thousand dissatisfied wives leave the harem and four hundred prisoners return to prison", a poem written by Bai Juyi, and this story comes from the period of "Zhenguan rule" of Emperor Taizong. Zhenguan period is an intoxicating historical picture: at that time, society was stable, cattle and horses were everywhere, people opened their doors at night, and there was a saying that "people can make up their clothes with bronze mirrors"; Take people as a mirror, you can know the gains and losses; Taking history as a mirror, we can know famous sayings and aphorisms, among which there are a group of sages and capable people like the grandson queen. Li Shimin brought the Tang Dynasty to an insurmountable height.
In 628 AD, Li Shimin gave birth to more than 3,000 ladies-in-waiting, and ordered them to "find a couple at will". In 633 AD, Li Shimin ordered nearly 400 prisoners to return to their hometowns to serve their sentences for one year, and then return to prison for punishment after the autumn harvest the following year. These prisoners were very grateful. After the next autumn harvest, all the prisoners were sent back to prison. Li Shimin was so happy that he pardoned all the prisoners on the spot. This is the famous "case of 400 prisoners returning to prison".
Bai Juyi has a poem praising the good governance of Emperor Taizong: 3,000 dissatisfied wives leave the harem and 400 death row inmates return to prison.