The Warring States Period (zhàn guó 战国,475――221BC) witnessed a great deal of wars and alliances among small states in China. At that time,in order to pursue their common interests in such hash situation,the State of Wei (wèi guó 魏国) and the State of Zhao (zhào guó 赵国) attempted to sign a treaty of alliance. As was usual at the time,the king of Wei had to send his son to Zhao as a hostage. A minister,Pang Cong (páng cōng 庞聪),was to accompany him.

Just before their departure,Pang Cong posed a strange question to the king: "If someone told you that there was a tiger in the street,would you believe it?"
"No,I wouldn't," replied the king.
"If two people said that, would you believe it?" the minister asked further.
"In that case,I would think twice about it," answered the king.
The minister went on, "if three people all said there's a tiger in the street,would you believe it then?"
"Of course I would," was the answer.
Then Pang Cong said: "It is strange,isn't it, that even when it's obvious there's no tiger in the street, you would believe there is one just because three people say so. Now, we're going to live in the State of Zhao that is far further away from Your Majesty's palace than the street. I'm sure there'll be a lot of rumors about me when I've gone. So I hope Your Majesty will be perceptive."
Hearing this,the king said," I know that. You can rest assured that I have every trust in you. Don't worry. Off you go."

After Pang Cong left with the prince,sure enough,his enemies spoke ill of him in front of the king. One after another,they told their stories. At first, the king paid no attention to them. But after a while,when he had heard enough rumors about the minister,he began to suspect Pang Cong. When the prince and the minister were finally freed as hostages,they returned to the State of Wei. The king didn't even summon Pang Cong to the palace!

From that story comes the idiom San Ren Cheng Hu. The idiom also suggests that gossip can be as ferocious as a tiger.

战国时期，中原各国间的战事、合盟不断。魏国与赵国正准备签订一份联盟协议。按照当时的惯例，魏王必须把太子送到赵国作为人质。 魏国大臣庞葱，将要陪魏太子到赵国去作人质。

庞葱临行前对魏王说：“如果有人说街市上出现了老虎，大王会相信吗？”
魏王道：“我不相信。”
庞葱说：“如果有第二个人说街市上出现了老虎，大王可相信吗？”
魏王道：“这样的话，我有些将信将疑了。”
庞葱又说：“如果有第三个人说街市上出现了老虎，大王相信吗？”
魏王道：“我当然会相信。”
庞葱就说：“街市上不会有老虎，这是很明显的事，可是经过三个人一说，好像真的有了老虎了。现在赵国离大王您的宫殿，比这里的街市远了许多。我确信议论我的人又不止三个。希望大王明察才好。”
魏王道：“我知道了。我保证会相信你的。不要担心。去吧。”

庞葱陪太子离开后，果然他的仇敌一个个都在魏王面前说他的坏话。起先，魏王并不理睬他们。但过了一阵子，他听了很多关于庞聪谗言后，他开始怀疑他了。当太子和庞聪终于被释，回国
后，魏王根本就不再召见庞聪了。

三人成虎这个成语就是由这个故事而来的，它指出谣言就像老虎那样可怕。

三人成虎 (sān rēn chéng hǔ)
【翻译】A repeated slander makes others believe.
【释义】三个人都说城市里有老虎，听的人就真的以为有老虎了。比喻说的人多了，就能使人们把
            谣言当事实。
【例句】谣传公司要裁员，搞得人心惶惶，真是三人成虎啊！
【近义词】众口铄金、道听途说
【反义词】眼见为实