How to connect the next sentence of Xia Yuhe on Daming Lake?

The next sentence in Xia Yuhe by Daming Lake is "The grass line is like silk, but the rock doesn't turn". This sentence came from the mouth of the princess, and my mother asked her after seeing her biological father before she died.

At that time, Ganlong traveled to Jinan incognito and met Xia because of a heavy rain. They fell in love at first sight, and after getting along sweetly for a period of time, Emperor Qianlong had to leave for some reason. Before leaving, he told his true identity and promised Xia that he would come back to pick her up. Later, Xia had her own flesh and blood. Unexpectedly, Gan Long was gone forever, so she decided to give birth to a child, named Xia Ziwei. Unfortunately, Xia died in his thoughts of Qianlong. Before he died, he told her the story of Wei Zi and told her to go to Beijing to find her father. He also told her that after seeing her father, she must ask, "Emperor, do you remember the summer by Daming Lake? Typha is like silk, but the rocks don't turn. "