《魏书·列传·卷六十五》
况且一旦纵敌，数世受其祸患，今天如若还师，令元颢重新修好防守设备，征兵天下，正是所谓养虺成蛇，悔之不及的行为。 
且一日纵敌，数世之患，今若还师，令颢重完守具，征兵天下，所谓养虺成蛇，悔无及矣。 
Moreover, once the enemy is released, his suffering will be suffered for several generations. If he returns to the teacher today, Yuan Hao will rebuild his defenses and recruit troops from all over the world. This is the so-called "raising snakes and regretting it".