What does it mean that the mountains and rivers are clear and bright?

"Mountains and rivers contain a clear glow" means that the scenery between mountains and rivers is like a clear light.

From Xie Lingyun in the Southern and Northern Dynasties, The Stone Wall Exquisite House Returns to the Lake.

The whole poem is:

The weather changes in the evening and early morning, and the scenery between scenes is like clear light. The lightness of the mountains and rivers makes people feel relaxed and happy, making people wander in the mountains and rivers and linger. It's still early from the valley, and it's too late when the boat gets on board. The Woods and valleys gather in the evening scenery, and the sunset clouds float in the night sky. Water chestnuts and lotus flowers echo in the blue river, and reed mats grow with wheat. Walking on the road in the south with dust, enjoying the doors and windows in the east happily. If you have fewer things to worry about, you will naturally feel that you have no worries, and you will feel very happy if you are in a carefree mood. These words are for people who want to keep fit. I hope they can keep fit in this way.

Translation:

The weather changes at dusk and early morning, and the scenery between mountains and rivers is like a clear lamp. The clear spirit of the landscape makes people feel relaxed and happy, making them swim in the landscape and forget to go back.

It was still early when I came out of the canyon, and it was too late when I got on the boat. Surrounded by Woods and valleys, there is a scene of dusk, and the sunset glow in the sky condenses and dances in the night sky. Water chestnut leaves and lotus flowers echo each other in the blue river, and Pu and Mai grow together. I am very happy to walk through the grass and trees on the south path and admire the doors and windows in the east. If you have less troubles, you will naturally feel that there is nothing to worry about, and you will feel very happy when you are in a good mood. Send these words to people who want to keep fit, hoping that they can use this method to keep fit.

Xie Lingyun is famous for being good at depicting wonderful scenery. This poem is about the scenery of boating on the lake, which is beautiful and pleasant. No matter how beautiful the handwriting is, it's useless. Everything has come out. It has its own elegant charm. It's really like water hibiscus, decorated with light makeup and swaying in the moonlight.

Xie Lingyun (385-433), a native of Taikang, Henan Province, and a native of Shining, Huiji (Shangyu, Zhejiang Province), was originally Chen Jun's Xie family. Posthumous title "Ke", the grandson of Xie Xuan, a famous soldier in the Eastern Jin Dynasty, was called "". He also attacked Gong to thank Kang Gong and Xie. A famous landscape poet in Liu and Song Dynasties was the pioneer of the landscape poetry school in the history of China literature.