"No, " the king answered.

    "Suppose a second man comes to say so, will Your Highness believe it?"

    "I'll begin to wonder."

    "Suppose a third man comes with the same report, will Your Highness take it as true?"

    "I believe I will."

    "Well, it is now as clear as daylight that no tiger dare go to the open market, but since three men have said the same thing, the presence of a tiger there becomes established.  Now, Handan is much further from our capital Daliang than the market is from the court, and those who talk behind my back will be more than just three.  When I'm gone I hope that Your Highness will not fail to judge what you will hear from them, and judge carefully."

    "I know how to judge."

    Then Pang Cong asked to be excused and bid farewell to the king, but after he had left calumnious words against him came at once to the king's ears.

    When the agreed period for the hostages was over, the heir-apparent returned.  Just as expected, Pang Cong was not given an audience by the king, who no longer trusted him.

Zhanguo Ce (Warring States Records)

    龐蔥與太子質於邯鄲。謂魏王曰：「今一人言市有虎，王信之乎？」王曰：「否。」「二人言市有虎，王信之乎？」王曰：「寡人疑之矣。」「三人言市有虎，王信之乎？」王曰：「寡人信之矣。」龐蔥曰：「夫市之無虎明矣，然而三人言而成虎。今邯鄲去大梁也遠於市，而議臣者過於三人矣，願王察之也！」王曰：「寡人自為知。」於是辭行，而讒言先至。

    後太子罷質，果不得見。

《戰國策•魏策二》