《后汉书·列传·光武十王列传》
四年春，皇上车驾近出，观览城市房屋，不久听说将到河内狩猎，刘苍上书劝阻道 ：臣听说时令，盛春农事很忙，不可聚众兴功。
四年春，车驾近出，观览城第，寻闻当遂校猎河内，苍即上书谏曰： 臣闻时令，盛春农事，不聚众兴功。
In the spring of the fourth year, the emperor's carriage was about to go out to inspect the city buildings. Soon after, it was heard that he was going to hunt in Henan. Liu Cang wrote a letter to dissuade him, saying: I have heard that in the busy spring season, farming is very busy, and it is not appropriate to gather people to start a project.