1. "Cong" is a preposition, which means "xiang", indicating that the destination of "coming" is Chu State. The source is "Farewell at Crossing Jingmen" by Li Bai of the Tang Dynasty.
2. Original text
I traveled far beyond Jingmen to travel from the Kingdom of Chu.
The mountains end with the plains, and the river flows into the wilderness.
Under the moon, there is a flying mirror, and the clouds form a sea tower.
I still feel sorry for the water in my hometown, and send my boat sailing thousands of miles away.
3. Interpretation
Traveling far away by boat, passing by Jingmen and arriving at the hometown of Chu State. The green hills gradually disappear, and the plains stretch as far as the eye can see. The Yangtze River surges into the vast wilderness. The moon reflecting on the river is like a flying mirror tomorrow; the clouds turn into blue and form a mirage. The water in my hometown is reluctant to part with me and sends me sailing all the way.