《汉书·传·贾邹枚路传》
晋文公亲近他的仇人勃千，而称雄于诸侯；齐桓公任用他的仇人管仲，而使天下诸侯纳入正轨。
夫晋文亲其仇，强伯诸侯；齐桓用其仇，而一匡天下。
The Duke Wen of Jin drew near to his enemy Bo Qian, and thus he was able to become chief among the feudal lords; the Duke Huan of Qi employed his enemy Guan Zhong, and thus he was able to lead the feudal lords of the world onto the right path.