Zhu Xiushi persuaded Lu Bei with the idea of the Sealing Skill. Lu Bei didn't want to start a war, but he also didn't want to return empty-handed from the treasure mountain and let Xiongchu reap the benefits.
Both sides backed down a bit. Lu Bei was allowed to go and persuade people from the Heavenly Sword Sect. No matter how his results turned out, he would have to leave Xiongchu after three days.
The three-day period was not randomly decided.
Lu Bei calculated that with an Earth Immortal's strength like Yuan Ji King, disappearing for three days would be equivalent to a closed retreat. It would attract little attention.
However, the original owner of the Sharira would be a bit tricky to deal with. It seemed that he had seen the Great Demon Immortal and might come knocking on the door directly.
To be safe, Lu Bei decided to bribe the Elder with mutal cultivation for three days and three nights.
Over these three days, he could dehumanize himself, or dehumanize the Elder.