On the "Cold Food Festival", why not make a fire to cook?

"Cold Food Festival", also known as "Smoke-free Festival", "Cold Food Festival" and "Hundred Five Festival", is held from the winter of the summer calendar to the next105th day and one or two days before Tomb-Sweeping Day. On this day, I don't smoke, I don't cook, I just eat cold food. Later, the folk gradually increased the customs of sweeping, climbing, swinging, squatting, hooking eggs and fighting eggs, which had a great influence on the folk and was once called "the biggest folk festival".

The origin of the "Cold Food Festival" is said to commemorate the introduction of the State of Jin in the Spring and Autumn Period. Jie Zhitui was a virtuous minister of the State of Jin, serving his son Zhong Er (later Jin Wengong). Later, civil strife broke out in the state of Jin, and his son Zhong Er was forced to flee abroad. Despite the difficulties, Jie Zhitui followed Zhong Er into exile. On the way to escape, Zhong Er was hungry, so Jiezhitui cut off his thigh and made soup for Zhong Er.

When Zhong Er became a monarch, he asked his men to announce their achievements and give them rewards. Many people reported their contributions and won awards. Jie Zhitui didn't say anything, so he didn't get a reward. He lived in seclusion in the mountains with his mother.