《旧唐书·列传·卷四》
窦建德跟他订立和约，魏刀儿就对他放松了防备，窦建德突然袭击，打败了他，吞并了他的全部地盘。
建德与之和，刀兒因弛守备，建德袭破之，又尽并其地。
Dou Jiande signed a peace treaty with him, and Wei Daoer relaxed his guard against him. Dou Jiande launched a surprise attack, defeated him, and annexed his territory. 