《资治通鉴·唐纪·唐纪四》
现在如果回师，他的势力就会重新振作起来，再加上各地互相联合，以后想要消灭他就难了！ 
今若旋师，贼势复振，更相连接，后必难图！ 
If we pull back our troops now, not only will his forces be revived, but they will also combine and unify together. It will be difficult to eliminate him in the future!