During the Han Dynasty, Su Wu was sent to Xiongnu and exiled by Khan to the North Sea to herd sheep. 10 years later, when the Han Dynasty approached the Huns, Khan still refused to let Su Wu return to Han. Chang Hui, who went to the Huns with Su Wu, secretly told Ambassador China about Su Wu, and designed Ambassador China to tell Khan that the Han emperor killed a wild goose when hunting, and a letter was tied to the goose's foot, telling him that Su Wu was herding sheep in a swamp. Upon hearing this, Khan only asked Su Wu to go back to Han. Later, people used Hongyan as a metaphor for letters and messengers.
Poetic imagery
The emergence of "Hongyan Biography" in the Pre-Qin and Han Dynasties. Since the Book of Songs, the "wild goose" has changed from a "companion" in people's daily life to a sentimental image in poetry, but there is no shadow of "Hongyan passing the book". There are four articles about geese in Chu Ci, and there is a sentence in Qu Yuan's Four Ren Mei: "It's hard to say because of the bird's return." Hong Xingzu pointed out: "Thinking of geese is a good way to touch the feelings of China people."
Although Qu Yuan himself did not point out that this "returning bird" that conveys love is Hongyan, although this returning bird only conveys "love", it is enough to inspire future generations' thoughts, which is not far from the Biography of Hongyan.