Which ancient poem does the lyrics of the Red Dust Inn come from?

The original inspiration of the Red Dust Inn comes from Vincent Fang's "Simple Poems under the Lamp", which is about reading Jin Yong's thoughts and then composing music by Jay Chou. Jay Chou said: In that concert in 2007, a short erhu performance was arranged before A Thousand Miles Away. At that time, I wrote a short melody to play as an erhu. This year, I made the melody I wrote at that time into a complete Chinese song, that is, this "Red Song".