《报燕惠王书》 / Letter in Reply to King Hui of Yan
《报燕惠王书》 enters the wiki through 《资治通鉴·周纪》80丨诸葛亮的偶像 到底有多厉害？ as 乐毅’s answer to 燕惠王 after Le Yi has fled to 赵国. The episode presents Yan Huiwang’s letter as a defensive accusation: he regrets the lost Qi occupation but asks why Le Yi abandoned Yan and how he can face 燕昭王’s former favor.
Le Yi’s reply is both refusal and restraint. He uses 伍子胥 to explain why a minister must read the ruler in front of him rather than rely on earlier merit, says he will not use 赵惠文王赵何’s favor to attack 燕国, and invokes the ethic that a gentleman does not speak evil after relations end. The source says 曹操 was moved to tears when reading the letter, making it part of Le Yi’s later reception as a model of exposed-command exit.