Sun Jian's great man's imperial seal bears the words "I am ordered by heaven to live forever". Why do people write it?

Qin unified China and was called "Qin Shihuang". Li Si, the prime minister, was ordered to be an emperor seal, and Li Si, the prime minister, was ordered to print the big characters "ordered by heaven, immortal", which looked like dragons, phoenixes and birds. Sun Shou, a jade worker in Xianyang, polished and carved stones into seals. It has been handed down from generation to generation, so it is called the "national seal"

Of course, it is addressed to Qin Shihuang. Others just got the jade seal to show authenticity.