《北史·列传·卷十六》
他还偷偷派人送一封密信给城中的源延伯，信上说： 大军就在附近，你要坚持尽忠，不要动摇。 
乃密遣人赍书间行与城中云： 大军在近，汝其奉忠，勿移其操。 
He also bribed a man to carry a confidential letter back to Yuan Yan Bo in the city. The letter stated, "The large army is close at hand. You must remain firm and loyal, and never allow yourself to waver."