《新唐书·列传·卷一百零六》
牛僧孺当了宰相，任命李绅为御史中丞，是看到他性格刚强急躁，容易出问题，又看到韩愈执著直率，就任命韩愈为京兆尹，兼任御史大夫，不需参谒台臣来激怒李绅。
僧孺辅政，以绅为御史中丞，顾其气刚卞，易疵累，而韩愈劲直，乃以愈为京兆尹，兼御史大夫，免台参以激绅。
When Niu Sengru became prime minister, he appointed Li Shen as Yushi Zhongcheng, because he saw that his character was so tough and irritable, and it was easy to cause problems. He also saw that Han Yu was so obstinate and straightforward, so he appointed Han Yu as Jingzhao Yin and concurrent Yushi Daifu, didn't need to pay homage to the minister to excite Li Shen.