Jia Dao, a poet of the Tang Dynasty, went to visit his friend Li Ning, but Li Ning was not at home. Jia Dao came all the way, hoping to see Li Ning and get the money to get back from him. At this time Everyone must have guessed that Jia Dao was extremely depressed. Not only did he miss out, but he might also risk begging on the street and go back. Fortunately, Jia Dao was a smart man, so he quickly put together a few poems and planned to find some money. A literary young man who was illiterate and admired poets greatly swindled some money. At that time, Jia Dao was riding on a donkey and remembered a sentence: "The bird stays in the tree by the pond, and the monk pushes the moon down the door." But he felt it was not good and wanted to change it to Knocking, but felt it was not good. So he made a "considering" gesture on the back of the donkey, and bumped into the honor guard of Yin and Han Yu in Jingzhao. Han Yu asked him why, and Jia Dao expressed his doubts. Han Yu asked him "Why do you think the monk came back in the middle of the night?" Jia Dao said: "As mentioned in the previous sentence, he just committed a lust and caution offense by the tree by the pool (for details, please refer to the film "Lust and Caution", in which the famous porn star Christi Chung bravely starred) Then he came back excitedly. In this case, he should have pushed him, because he didn't want his master to know that he was staying out at night." Han Yu said, "No, no, if he comes back secretly, it will be more inappropriate and cause trouble. People doubt it. If he is a smart monk, he will knock on the door as if nothing has happened." Jia Dao praised: "What an insight!" Then he found a piece of paper and wrote the poem down, and specially asked Han Yu to be aside. Note: "It's better to knock here! Han Yu" and expressed his admiration, and then he thanked and left.

The next day, Jia Dao shouted loudly on the roadside: "Jingzhao Yin Han Yu" Mr. signed it himself!" Finally he returned home safely. The word "examination" became a popular story. Later generations called the serious study of knowledge "examination".