《北史·列传·卷七十四》
他的弟子问其中的原因，道研说 ：每次见到苏府君，他就直接把我带到青云之中，哪有可能谈论地上俗事？ 
其弟子问其故，研曰： 每见府君，径将我入青云间，何由得论地上事。 
His disciples asked the reason why, and Daoyan said: Every time I see Prefect Su, he takes me directly to the QIngyun, how could it be possible to talk about worldly affairs?