《资治通鉴·隋纪·隋纪七》
窦建德对高士达说： 我观察了不少隋将，善于用兵的莫过于杨义臣了，如今他灭掉了张金称乘胜而来，锐不可挡，请您率兵避开他，让他欲战不得，耗费时间，将士疲劳厌倦，然后我们再乘机袭击他，杨义臣才能被攻破，否则，恐怕您不是他的对手。 
建德谓士达曰： 历观隋将，善用兵者无如义臣。今灭张金称而来，其锋不可当。请引兵避之，使其欲战不得，坐费岁月，将士疲倦。然后乘间击之，乃可破也。
Dou Jiande said to Gao Shida: "I have observed many Sui generals, and none is more skilled in warfare than Yang Yichen. Now that he has triumphed over Zhang Jincheng and gained momentum, it would be unwise to confront him head-on. I suggest you withdraw your troops to avoid a direct clash. This will frustrate Yang Yichen and waste his time. As his soldiers grow weary and exhausted, we can seize the opportunity to strike back. Only then will we have a chance of defeating Yang Yichen. Otherwise, I fear that you may not be his match."