《隋书·帝纪·卷四》
天子的使臣奉命出使，来到海东，沿途停留的地方，多经过属国的境土。而高丽竟然堵塞道路，拒绝帝王派出的使臣，简直没有侍奉君上的心思，这难道是做臣下应有的礼节！
輶轩奉使，爰暨海东，旌节所次，途经籓境，而拥塞道路，拒绝王人，无事君之心，岂为臣之礼！
Imperial envoys were sent to the sea to the east, and most of the places they stopped along the way were vassal states. However, Goguryeo blocked the roads and refused to accept the envoys sent by the emperor, showing no intention of serving the emperor. Is this the etiquette that a subject should have?