李白在四川的象耳山求学时，学业还没有完成，他就离开了。
在回家的路上，他经过一条河，看到一位老妇正在河边磨一根铁杵。
李白好奇地问她：“您在做什么呢？”
老妇人停下手中的活儿，微笑着回答说：“我想把这根铁杵磨成一根细针。”
李白听了非常惊讶，他难以置信地看着那根粗大的铁杵和老妇手中细细的石头。
他觉得这是一件不可能完成的任务。
老妇看出李白的疑惑，便对他说：“只要我每天都坚持磨下去，总有一天会成功的。”
李白深受感动，他被老妇的决心和毅力所打动。
于是，他决定返回学堂，继续完成他的学业。
从那以后，李白不再轻易放弃任何事情。
他知道只要有决心、有毅力，就一定能够克服困难，实现自己的目标。
这个故事后来被人们简化为成语“磨杵成针”，用来比喻只要能努力且坚持去做，无论多么困难的事，都可以完成。
When Li Bai was studying at Elephant Ear Mountain in Sichuan, he left before completing his studies.
On his way home, he passed by a river and saw an old woman grinding an iron pestle by the riverbank.
Out of curiosity, Li Bai asked her, "What are you doing?"
The old woman stopped her work and smiled, replying, "I want to grind this iron pestle into a fine needle."
Li Bai was astonished. He looked at the large iron pestle and the small stone in the old woman's hand with disbelief.
He thought it was an impossible task.
Perceiving Li Bai's doubts, the old woman said to him, "As long as I keep grinding every day, I will succeed someday."
Deeply moved, Li Bai was inspired by the old woman's determination and perseverance.
So, he decided to return to school and continue his studies.
From then on, Li Bai never gave up easily on anything.
He knew that with determination and perseverance, one could overcome any difficulty and achieve their goals.
This story later became the idiom 'grinding an iron pestle into a needle', symbolizing that with hard work and persistence, even the most difficult tasks can be accomplished.
