This is a story from Three Kingdoms.
During the siege of Fancheng City, General Guan Yu was struck in the right arm by a poisoned arrow. After the arrowhead was removed, it was discovered that the poison had already seeped into the bone. His men urged him to retreat to Jingzhou for treatment, but Guan Yu, determined to capture the city, refused.
As his wound worsened, scouts were sent to find a skilled doctor. One day, the renowned physician Hua Tuo arrived by boat specifically to treat him. When asked about the procedure, Hua Tuo suggested securing Guan Yu's arm to a post and covering his eyes to prevent fear. Guan Yu laughed and declined, instead ordering a feast in Hua Tuo's honor.
After sharing wine, Guan Yu began a game of chess. He then extended his injured arm to the doctor and said, "It is at your disposal. I have no fear." Hua Tuo cut open the flesh and scraped the bone with a scalpel. The onlookers covered their eyes in horror, but Guan Yu continued drinking and playing chess calmly, even as blood filled a basin.
Once the poison was fully removed, Guan Yu stood up, moved his arm freely, and praised Hua Tuo as a "magic doctor." Hua Tuo, in turn, marveled at Guan Yu's fortitude, declaring him a "magic general" unlike any patient he had ever seen.