Zhang Liang was originally a noble of the Han state, surnamed Ji, but after a failed assassination attempt on the First Emperor of Qin, he fled to Xiapi to hide and changed his name to Zhang Liang.
One day, Zhang Liang was strolling on the Yi Bridge in Xiapi when he met an old man in brown clothes. The old man's shoe had fallen under the bridge, and seeing Zhang Liang approach, he called out, "Hey, young man! Go pick up my shoe for me!"
Zhang Liang was quite displeased, but seeing how old the man was, he went down the bridge and picked up the shoe. When the old man saw this, he said to Zhang Liang, "Come! Put it on for me!"
Zhang Liang was quite displeased, but then thought, since he had already picked up the shoe, why make a fuss? So he respectfully helped the old man put it on. The old man stood up, didn't say a single word of thanks, and walked away.
Zhang Liang stared blankly at the old man's retreating figure, guessing that this elder must be someone of significance. Sure enough, after walking about a li, the old man turned back and said:
"You're a promising young man, worth my guidance. Meet me on the bridge in five days' time, in the morning."
Zhang Liang immediately agreed.
On the fifth morning, Zhang Liang arrived at the bridge. The old man was already there and said angrily, "When meeting an elder, you should arrive early. Come back in five days, and be earlier!" After another five days, Zhang Liang rose early and rushed to the bridge, but the old man was there first again. The old man said, "You are late again. Come back in five days."
Five days later, Zhang Liang resolved to arrive before the old man this time. So he groped his way to the bridge just after midnight and waited. At daybreak, he saw the old man hobbling onto the bridge and quickly went to support him. The old man said happily, "Young man, that's the way it should be!"
The old man said, taking out a copy of *The Art of War by Taigong* and handing it to Zhang Liang, "You must study this book diligently. Master it thoroughly, and you can become a teacher to emperors."
After Zhang Liang expressed his gratitude to the old man, the elder strode away without a backward glance. Later, Zhang Liang studied the *Taigong's Art of War* with great success, becoming a key strategist under Liu Bang, the first emperor of the Han Dynasty, and earning great merit for his contributions to the founding of the Han empire.
Later, the idiom "The Youngster Is Worth Teaching" is used to describe a promising young person who can be nurtured.
Source: *Records of the Grand Historian*, "Biography of the Marquis of Liu"
Meaning of the Idiom: Later, the Chinese idiom "孺子可教" came to describe a promising young person who can be nurtured.