《后汉书·列传·班梁列传》
第二年，皇帝下诏令说： 过去匈奴独霸西域，侵犯河西，永平末年，白天也要把城门关起来。
明年，下诏曰： 往者匈奴独擅西域，寇盗河西，永平之末，城门昼闭。
The following year, the emperor issued an edict saying: In the past, the Xiongnu had sole control over the Western Regions, and encroached on the Hexi Corridor. At the end of the Yongping reign period, the city gates had to be closed even during the day.