《资治通鉴·晋纪·晋纪二十一》
可以先让宰相给他写一封亲笔信，向他表示恳切的诚意，为他分析成败趋势，他就一定会率兵返回了；如果不听，那就由皇上亲自下达手诏；再不听，就应当用正义之师去制裁他。
令相王与手书，示以款诚，为陈成败，彼必旋师；若不从，则遣中诏；又不从，乃当以正义相裁。
Can have the prime minister first write him a personal letter, to sincerely express his goodwill, and analyze the trend of success and failure for him. He will definitely lead his troops back; if he does not listen, then the emperor will personally issue an imperial edict; if he still does not listen, then a righteous army should be sent to punish him.