《新唐书·列传·卷一百四十四》
第二年，诏令尚书右丞崔余庆持节总护定襄等三都督前往讨伐。奚害怕了，乞降，斩杀其王匹帝。
明年，诏尚书右丞崔馀庆持节总护定襄等三都督讨之，奚惧乞降，斩其王匹帝。
The next year, it was ordered that the Right Assistant Minister of the Minister, Cui Yuqing, should take the order and lead the Protector generals in Dingxiang to fight against them. Xi was afraid and begged to surrender, he beheaded their king Pi Di.