《汉书·传·匈奴传上》
单于喜欢王乌，假装答应王乌说： 我为你的缘故派太子到汉朝去做人质，以求与汉朝和亲。 
单于爱之，阳许曰： 吾为遣其太子入质于汉，以求和亲。 
The Chanyu liked Wang Wu and pretended to agree with Wang Wu, saying: "I will send the prince to the Han Dynasty as a hostage for your sake, in order to seek marriage with the Han Dynasty.