During the Warring States Period, King Hui of Zhao got a treasure from Chu named He Shibi. When Zhao Haoqi, the king of Qin, heard about this incident, he wrote to Zhao Huiwang that he was willing to exchange fifteen cities for Cui. When Zhao met Lin Xiangru, Lin Xiangru expressed his willingness to take Choi to the State of Qin. If the prince of Zhao gets the city, he will give it to the king of Qin, otherwise, he will bring it back.
After Lin Xiangru came to the state of Qin, he gave this piece of jade to the king of Qin. King Qin Zhao was very happy, but he didn't mean to give the city to the prince of Zhao. Lin Xiangru said to the king of Qin, this jade has a small flaw, and I want to show it to the king of Qin. Taking Baoyu back, he went to the pillar and said that the prince of Zhao was worried that Qin would stand on its own feet and would not give Baoyu to the city. After my persuasion, he agreed. The King of Zhao fasted for five days and asked me to support the wall to show my respect for Qin.
The king, on the other hand, has simple manners and no sincerity to exchange. If the king must rob Baoyu, I'd rather hit my head on the post with Baoyu. Qin had no choice but to take out a map and draw fifteen cities for Zhao.
Lin Xiangru was worried that the king of Qin was just pretending to deal with it, so he offered to fast for five days and set up a "nine guests" ceremony as a solemn exchange. The king of Qin had to agree. Lin Xiangru sent his entourage with Cui and returned to Zhao by the original road. When the exchange ceremony was held, Lin Xiangru told the king of Qin that Cui was sent back to Zhao, thus preserving Cui.