What's the poem behind "Keep hate as a rainy night in spring, add spring to the river"?

"From hate to spring rain. Add to the Chunjiang River and row to the east. Weak willows can't even keep the boat because you are worried. " (Sean Song Yan Zheng's "Die Hua Lian Biefan Nanbo") On the eve of parting, the spring rain continued; When the spring river rises, best friends go boating with the eastward flowing river. The weak willow branches on the river bank couldn't tie the boat that was going, so "I" had to listen to the sound and send my friends away.