What is the meaning of this ancient poem by Wen Xiu during the Dragon Boat Festival and the Tang Dynasty?

The Dragon Boat Festival on the fifth day of the fifth lunar month is one of the folk "three festivals a year". According to legend, this day was the day when Qu Yuan, the first great man in China, committed suicide. Later generations wronged him, so they threw zongzi into the river for sacrifice and rowed a boat to save him, which became the custom of solar eclipse and dragon boat race on the Dragon Boat Festival. The author's quatrain raises a thought-provoking question (that is, the moral of this ancient poem): although there are all kinds of praises and sacrifices from later generations, tragedies like Qu Yuan's sinking into the river have happened after all, and such grievances cannot be simply washed away.

Dragon Boat Festival

Dynasty: Tang Dynasty

Author: Wen Xiu

Original text:

The festival is divided into Dragon Boat Festival, which is said to be Qu Yuan.

I can laugh at the emptiness of the Chu River, but I can't wash it straight.