司馬遷
The "Letter to Ren An" was written by Sima Qian in reply to Ren An in response to the latter's involvement in Crown Prince Liu Ju's rebellion in 91 BC. This is the last record of Sima Qian in contemporary documents. The letter is a reply to a lost letter by Ren An to Sima Qian, perhaps asking Sima Qian to intercede on his behalf as Ren An was facing execution for accusations of being an opportunist and displaying equivocal loyalty to the emperor during the rebellion. In his reply, Sima Qian stated that he is a mutilated man with no influence at court. Some later historians claimed that Sima Qian himself became implicated in the rebellion as a result of his friendship with Ren An and was executed as part of the purge of the crown prince's supporters in court; however, the earliest attested record of this account dates from the 4th century. Moreover, it has also been pointed out that Sima Qian would have been reluctant to render substantive aid to Ren An, given the severe consequences that he suffered for supporting General Li Ling, as well as Ren An's failure to act on his behalf during the Li Ling affair. Although there are many theories regarding the exact dating as well as the true nature and purpose of the "Letter to Ren An", one common interpretation suggests that the letter, in part, tacitly expressed a refusal to play an active role in securing a reduced punishment for Ren An.