The origin of jiaozi is the writing of 30 characters.

Jiaozi, formerly known as Joule, is said to have been first invented by Zhang Zhongjing, a medical saint in China. The story of his "Quhan Joule Decoction" has spread among the people to this day.

According to legend, when Zhang Zhongjing was the magistrate of Changsha, he often treated the people. One year, when the local plague was prevalent, he made a cauldron at the entrance of Yamen, giving up medicine to save people, which was deeply loved by Changsha people. After Zhang Zhongjing retired from Changsha, he just caught up with the winter solstice and walked to the shore of the Baihe River in his hometown. He saw that many poor people were hungry and cold, and their ears were frozen. It turned out that typhoid fever was prevalent at that time and many people died. He was very upset and determined to treat them. When Zhang Zhongjing came home, many people sought medical treatment. He is as busy as a bee, but he always remembers those poor people with frozen ears. He followed Changsha's example and told his disciples to build a medical shed and cauldron in an open space in Dongguan, Nanyang, and open it on the day of winter solstice to send medicine to the poor to treat their injuries.

Zhang Zhongjing's Quhan Joule Decoction is a summary of more than 300 years of clinical practice in Han Dynasty. Its practice is to put mutton, pepper and some cold-dispelling medicinal materials into a pot and cook them, then take them out and chop them up, make them into ear-shaped Joules with flour bags, put them into a pot and cook them and distribute them to patients seeking medicine. Everyone has two charming ears and a bowl of soup. After eating Quhan decoction, people feel feverish all over, their qi and blood are smooth, and their ears are warm. People eat from the solstice of winter to New Year's Eve, fighting typhoid fever and curing frozen ears.

Zhang Zhongjing didn't give up taking medicine until New Year's Eve. On the first day of New Year's Day, people celebrate the New Year and the recovery of rotten ears. They cook food for the New Year like burnt ears and eat it on the first morning. People call this kind of food "jiaozi", "jiaozi" or "flat food" and eat it on the solstice of winter and the first day of New Year to commemorate the day when Zhang Zhongjing opened the shed to deliver medicine and treat patients.

Zhang Zhongjing's history is nearly 1800 years ago, but his story of "Quhan Joule Decoction" has been widely circulated among the people. On the solstice of winter and the first day of New Year's Day, people eat jiaozi, and they still remember Zhang Zhongjing's kindness in their hearts. Today, we don't need charming ears to cure frozen ears, but jiaozi has become the most common and favorite food for people.