It means that when rising clouds encounter cold air, they form rain, and when the temperature drops at night, dew condenses into frost. Gold is produced in the water of Lijiang, and jade is produced in the Kunlun Mountains.
This sentence comes from the "Thousand Character Essay", which was compiled by Zhou Xingsi, the minister of Sanqi in Liang Dynasty during the Southern and Northern Dynasties.
Keynote explanation:
Clouds, rain, frost, and dew are all natural phenomena, and their formation is regular, which has also been confirmed by modern technology. China is extremely rich in products, and precious gold and jade are just their representatives. In the lives of ancient people, both substances played very important roles.
Gold and jade are very precious and rare natural products. Gold is the first of a hundred golds. The ancients believed that gold could ward off evil spirits and avoid evil, so gold was often used as jewelry. The most famous alluvial gold producing area in China is in Lishui, which is Lijiang in Yunnan. Lijiang has been called the Jinsha River since ancient times because of its golden sand.
According to legend, jade is the result of mountains and rocks that have been transformed by the essence of the sun and the moon for thousands of years. Therefore, there is a saying that "watching the auspicious clouds will tell you that there are beautiful jade in the mountains." Good jade is called warm jade and feels warm in your hand. Kunlun Mountain is famous for the production of beautiful jade. It was the main source of jade mining in ancient China. It is also the legendary place where gods live. The Queen Mother's cave is said to be above West Kunlun.
Extended information:
Thousand-Character Essay, a rhyme composed of one thousand Chinese characters compiled by the Sanqi Shilang of the Liang Dynasty and Zhou Xingsi in the Northern and Southern Dynasties (before the Sui and Tang Dynasties, it did not rhyme , non-compatible writing is called "pen", not "wen"). Emperor Wu of Liang (502-549) ordered people to select 1,000 non-repeating Chinese characters from Wang Xizhi's calligraphy works, and ordered Zhou Xingsi, the minister of Waisanqi, to compile it into a document.
The full text is a four-character sentence, with neat contrasts, clear organization, and brilliant literary talent. The Sentences of "The Thousand-Character Classic" are as plain as words, easy to recite and memorize. It has been translated into English, French, Latin and Italian versions. It is a children's enlightenment book with great influence in China.
Baidu Encyclopedia - Thousand Character Essay