Why are the door gods in China folk customs Weichi Gong and Qin?

1. The first version. After Li Shimin proclaimed himself emperor, he often dreamed that the ghosts of Li and Li Yuanji came to kill him, which made him sleepless all night and nervous. So the eldest grandson gave him an idea: let Qin stand guard. These two men are fierce dissidents and euphemistically involved in the killing of Li Er. Maybe the ghost of Li Er was afraid of them, so he never harassed Li Shimin again. What happened in the court soon spread to the people. The common people followed suit and put their portraits on the doors to ward off evil spirits. Over time, this has become a custom. And Qin also gradually became a keeper.

2. The second version. The Journey to the West story, one of the four classical novels. The old Dragon King of Jinghe River near Chang 'an made a bet with a fortune teller, and the result was that his temper was broken. The Jade Emperor was furious and ordered Wei Zhi, the minister under Emperor Taizong, to behead the old dragon king at three o'clock in the afternoon. Of course, the old dragon king was afraid, so he asked Taizong in his dream. Emperor Taizong agreed, and the next day, he pestered Wei Zhi to play chess, thinking that this would stall Wei Zhi. Unexpectedly, at three o'clock at noon, Wei Zhi dozed off. Li Shimin didn't know that Wei Zhi was beheaded in his dream. The old dragon king thinks that Li Shimin broke his promise and harassed him every day after his death. Persuading Qin to keep watch really worked. But people are made of meat after all, and the two generals can't be night owls every day. So, Li Shimin asked his men to draw a portrait of the second general and put it on the door. The result still worked. As a result, this move began to spread among the people, and Qin Qiong and Wei Chijingde became door gods.