沧浪之水清兮

From 《楚辞·渔父》 (Chu Ci, The Fisherman, ca. 3rd c. BCE), the Fisherman's reply to Qu Yuan: 沧浪之水清兮，可以濯我缨；沧浪之水浊兮，可以濯我足 (When Canglang's water is clear, I wash my hatstrings; when it is muddy, I wash my feet). 缨 = the silk tassels of an official's hat, symbol of office; washing them requires pure water, i.e., an honorable regime. A Daoist argument for adapting to the times instead of destroying oneself for principle. Also quoted in 《孟子·离娄上》 as a children's song that Confucius overheard and commented on.

Always paired with 沧浪之水浊兮. 兮 (xī) is the Chu-dialect exclamatory particle, characteristic of all 楚辞 (Chuci) prosody. The Suzhou scholar's garden 沧浪亭 (Canglang Pavilion, 1044) is named for this passage.