《旧唐书·列传·卷四》
隋炀帝大业七年，朝廷招兵征讨高丽，郡里挑选勇敢优异的人当小帅，于是委任窦建德为二百人长。
大业七年，募人讨高丽，本郡选勇敢尤异者以充小帅，遂补建德为二百人长。
In the seventh year of the Daye reign of Emperor Yang of Sui, the imperial court conscripted soldiers to fight in Goguryeo. The county selected brave and capable men to be petty officers, and Dou Jiande was appointed to lead two hundred men.