There was no electricity in ancient times, and oil lamps were used for lighting at night. /kloc-kerosene gradually became popular in China after the late 8th century. At night, the oil of electric lamps is vegetable oil, which is commonly used in cooking. Therefore, the literal translation of this sentence is to advise parents all over the world not to stir-fry with oil, and leave the oil to their children to study by lighting at night. It means advising parents all over the world to save some money in other aspects of their lives and use the money saved for their children's education. A modern popular slogan echoes it: no matter how poor you are, you can't be poor in education.