春秋时代，有一个国家叫鲁国。
有一天，鲁国发生了一场内乱，鲁昭公被迫离开了自己的国家，逃到了齐国。
齐景公是齐国的国王，他见到了鲁昭公，问他：“你年纪轻轻就失去了国家，这是什么原因呢？”
鲁昭公回答说：“我年轻的时候，有很多人爱护我，但我没有对他们好；也有很多人给我建议，我也没有听从。结果，我对内没有人帮助，对外也没有人支持。现在，真心帮助我的人已经很少了，反而有很多人讨好和奉承我。这就像是秋天的蓬草，虽然看起来还很漂亮，但根部已经干枯，一旦有风吹来，就会被连根拔起。”
齐景公觉得鲁昭公说的话很有道理，就告诉了他的大臣晏子，并问：“如果帮助鲁昭公回到鲁国，他会成为一个贤明爱民的君王吗？”
晏子回答说：“不会的。愚昧的人常常自满，不贤的人也常常以为自己很能干。就像掉进水里和迷路的人一样，他们原本就不注意路径方向，直到溺水了才知道探水路，迷路了才会向人问路。这就像是国家面临危难时，才急忙去制造兵器，被食物塞住喉咙了，才急着挖井取水来喝。虽然行动很快，但还是来不及了。”
后来，人们就把晏子后面说的这段话，引申为“临渴掘井”这句成语。
这个成语比喻事到临头才急忙准备应付，但已经来不及了。
In the Spring and Autumn period, there was a country called Lu.
One day, an internal rebellion occurred in Lu, and Duke Zhao of Lu was forced to leave his country and flee to Qi.
King Jing of Qi was the king of Qi, he saw Duke Zhao of Lu, and asked him: "You lost your country at a young age, what is the reason for this?"
Duke Zhao of Lu replied: "When I was young, many people loved me, but I was not good to them; many people also gave me advice, but I did not listen. As a result, I have no one to help me inside, and no one supports me outside. Now, there are few people who sincerely help me, but many people flatter and fawn on me. It's like the autumn reed grass, although it still looks beautiful, its roots are already withered. Once the wind blows, it will be uprooted."
King Jing of Qi thought that what Duke Zhao of Lu said made sense, so he told his minister Yan Zi and asked: "If we help Duke Zhao of Lu return to Lu, will he become a wise and loving king?"
Yan Zi replied: "No. Foolish people often feel complacent, and unworthy people also often think they are capable. Just like someone who falls into the water or gets lost, they don't pay attention to the direction until they drown before they know how to explore the waterway, and they only ask for directions when they get lost. It's just like when the country is in danger, rushing to make weapons, and when their throat is blocked by food, they rush to dig a well to drink water. Although they act quickly, it's too late."
Later, people extended the words that Yan Zi said later to the idiom 'digging a well when thirsty'.
This idiom means preparing to deal with something only when it happens, but it's too late.
