When studying, you must read until midnight when the bright moon sets in the west. When practicing calligraphy, you must study hard and practice so that the sky is cloudless. Searching relevant information shows that when the sound of books is read and the moon sets in the middle of the night, the pen array sweeps away thousands of miles of clouds, which means that when reading, one must wait until the third watch of the night and the bright moon sets in the west. When practicing calligraphy, one must study hard and practice hard to sweep away thousands of miles of clouds. This couplet is used by many calligraphers and writers as their motto. The calligrapher Zha Shiyu regarded reading the sound of the book at the end of the third night as his lifelong pursuit.