Summarize the main idea of Han's story in about 80 words and talk about the center of the story.

Yong Dong was born in Qiancheng, Han Dynasty. Yong Dong's mother died at an early age and lived with her father. Father plowed the land, and Yong Dong followed his father with a cart. Later, his father died and there was no money to bury him. Yong Dong had to sell himself into slavery and exchange money for his father's funeral. Knowing Yong Dong's virtue, his master gave him ten thousand pence to go home. After three years of mourning at home, Yong Dong is going to pay his debts as a slave in his master's house. On the way to my host's house, I met a woman and said to him, "I would like to be your wife." (Yong Dong) went to the host's house with her. The host said to Yong Dong, "Here's the money (no need to pay it back)." Yong Dong replied, "Thanks to your kindness, my father's body was collected and buried. Although Yong Dong is an ordinary person, he must try his best to undertake labor services to repay your great kindness. " The host said, "What can your wife do?" Yong Dong said, "I can knit." The host said, "In that case, let your wife help me knit a hundred fine silks." So Yong Dong's wife knitted silk for her master's house, and it was finished in ten days. The Weaver Girl walked out of the door of the knitting room and told Yong Dong, "I am the Weaver Girl in the sky. Because you are very filial, God sent me to earth to help you pay your debts. Then I flew away in the air, and I don't know where I went.