The story of ancient literati's careful words and sentences

Jia Dao took the imperial examination in Beijing for the first time. One day, he thought of two poems on the donkey's back: "Birds stay in trees by the pool, and monks knock at the door of the moon." At first, he wanted to use the word "push" and "knock". After repeated thinking, he recited on the donkey's back and kept pushing and knocking. At that time, Han Yu temporarily acted as the local governor of Beijing. The onlookers were surprised by the gestures they kept making. So they were shoved in front of Han Yu by the attendants around (Han Yu). Jia Dao answered the poem he was brewing in detail, and he was uncertain whether to use the word "push" or "knock". He left the immediate things and didn't know to avoid it. Han Yu stopped thinking for a long time and said to Jia Dao.