From Liu Xin's Miscellanies of the History of the Han Dynasty in Xijing, Volume II, the original text: study hard, have a candle, neighbors don't catch it, always cross the wall to attract its light, and send books to reflect it. City people can't read their surnames. They have money at home and many books. Therefore, Heng is cooperating with him, not claiming compensation. The master asked Heng strangely, and Heng said, "May the master read all the books." The host sighed, gave books and became a university.

Translation:

Kuang Heng is diligent and studious, but there is no candle lighting at home. There is a candle next door, but the candle next door can't penetrate, so Kuang Heng cut a hole in the wall to bring in the light from his neighbor's house, so that the light can shine on the book and read. There is a large family in the same town who is illiterate, rich and has many books. Kuang Heng went to his home to work hard as an employee, but he didn't get paid.

The host was surprised and asked him. He said, "I hope to get your book and read it through." Hearing this, the master sighed deeply and lent him the book. Finally, Kuang Heng became a learned man.

Revelation:

Praised Kuang Heng's courage to overcome difficulties and study hard; Set a good example for us to study hard. No matter how hard the conditions are, they cannot be an obstacle to learning. Insufficient conditions can create conditions. The key to learning lies in willingness to learn and strong will.

Later generations refer to "digging the wall down, stealing light, digging the wall to borrow light, borrowing light" and so on, and sometimes it is extended to ask for advice from others. The idiom in this story is to steal the light (the protagonist Kuang Heng is eager to learn). On the surface, this idiom means reading by the neighbor's candlelight. Now this idiom is used to describe hard work.