wait till the yellow river runs clear water
As a Chinese idiom, the Pinyin is s ì h é zh ī Q ī ng, which means waiting for the Yellow River to clear. It's a metaphor for not being able to achieve what you expect. From Zuo Zhuan, the eighth year of Xianggong.
The origin of Idioms
In the eighth year of Xianggong in Zuozhuan, it is said in Zhoushi: "when the river is clear, how will life be?"
Idiom usage
Contraction; predicate; derogatory
Examples
What a "~" it is! On the bridge by Ye Shengtao
wait till the yellow river runs clear water
table delicacies from land and sea - shān zhēn hǎi wèi
Bird's way and sheep's intestines - niǎo dào yáng cháng