What is a three-character sticker?

It's a Sanxi Hall law post, right? "Sanxi Hall" is located in hall of mental cultivation West Warm Pavilion of the Palace Museum. It is the study of Emperor Qianlong of the Qing Dynasty. Emperor Qianlong was knowledgeable and good at poetry, especially calligraphy. Gan Long searched for famous stickers all over the country many times. He put Wang Xizhi's Sunny Gua in the Fast Snow, Wang Xun's Yuan Bo Gua and Wang Xianzhi's Mid-Autumn Gua in his study as three rare treasures, and named his study "Sanxi Hall". In order to spread calligraphy to the whole country, he later ordered the ink color of the above three calligraphy posts and the original calligraphy collected by the Imperial Palace to be compiled into a large-scale collection called Sanxi Hall Fa Tie. Sanxi Hall, which was accomplished in the 12th year of Qianlong reign in Qing Dynasty, was edited by Liang et al., with a collection of 32 volumes, including more than 30 famous calligraphers/kloc-0. Beijing Qiongdao (now Beihai Park) is also engraved with "Sanxi Hall Fa Tie" for the literati to read and copy. Wang Xizhi's "Looking at the Fast Snow" has four lines and 28 characters, which is Wang Xizhi's work after forty years old. At that time, it was just a handwritten note, named after the words "eyes looking at the snow" in the post. This post is free and easy with a pen, and the font is Shu Lang. It is a famous article in Wang Ti's running script. Later generations said that "Yue Long Mountain Gate, Tiger Lying in the Wind Pavilion". Wang Xun's Yuan Bo Tie has six lines and 47 words, which is a typical running script of Jin Dynasty. Its content is narrative, and the name of the post comes from the word "Yuan Bo" in the first sentence of the post. The pen of "Yuan Bo Post", dancing and dancing, is an excellent cursive work. Wang Xianzhi's Mid-Autumn Festival post, full text * * * 22 words and four lines. Wang Xianzhi is the seventh son of Wang Xizhi, and his calligraphy is influenced by his father. He further sublimated and refined Wang Tixing's brushwork. This post is close to cursive script, and Wang Xianzhi's pen is like flowing water, reflecting each other, and the handling of fonts is perfect. This post is his work after the age of 50, and it is a handwritten note. Wang Xizhi is known as "the sage of books" and Wang Xianzhi is known as "the sage of Asia".