It is mentioned by Abu Ja’far Al Iskafy in the book...

It is mentioned by Abu Ja’far Al Iskafy in the book ‘Al-Maqamaat’ in the virtues of Amir Al-Momineen-asws, may the greetings be upon him-asws Letter 55 – And from a letter of his-asws to Muawiya Letter 56 – And from a bequest (speech) of his-asws advising Shurayh Bin Hany by it when he-asws made him to be (a commander) upon his-asws vanguard to Syria Letter 57 – And from a letter of his-asws to the people of Al-Kufa during his journey from Al-Medina to Al-Basra Letter 58 – And from a letter of his-asws to the people of various localities, narrating in it what had flowed between him and the people of Siffeen Letter 59 – And from a letter of his-asws to Al-Aswad Bin Qutba commander of the army of Hulwan Letter 60 – And from a letter of his-asws to the office bearers, those the army passed by their offices Letter 61 – From a letter of his-asws to Kumeyl Bin Ziyad Al-Nakhaie, and he was his-asws office bearer upon Hayt, and he-asws disliked upon him of his neglect in defending from the crossing of the enemy army by him seeking the raids Letter 62 – And from a letter of his-asws to the people of Egypt, (sent) with Al-Ashtar, may Allah-azwj have Mercy on him, when he-asws had placed him in charge of its emirate Letter 63 – And from a letter of his-asws to Abu Musa Al-Ashari, and he was a governor upon Al-Kufa, and his discouraging the people from coming out to him-asws when he-asws called them to battle the companions of the camel Letter 64 – And from a letter of his-asws to Muawiya in reply to his letter Letter 65 – And from a letter of his-asws also to him (Muawiya) Letter 66 – And from a letter of his-asws to Abdullah Bin Al-Abbas, and its mention has preceded differently to this report Letter 67 – And from a letter of his-asws to Qusam Bin Al-Abbas, and he was his-asws office bearer upon Makkah Letter 68 – And from a letter of his-asws to Salman Al-Farsi-ra, may Allah-azwj have Mercy on him-ra, before the days of his-asws caliphate Letter 69 – And from a letter of his-asws to Al-Haris Al-Hamdany Letter 70 – And from a letter of his-asws to Sahl Bin Huneyf Al-Ansari, and he was his-asws office bearer upon Al-Medina, in meaning a group of its inhabitants who had joined with Muawiya Letter 71 – And from a letter of his-asws to Munzir Bin Al-Jaroud, and he had embezzled in some of what he had overseen from his-asws administration Letter 72 – And from a letter of his-asws to Abdullah Bin Al-Abbas Letter 73 – And from a letter of his-asws to Muawiya Letter 74 – And from an alliance treaty he-asws wrote between Al-Yemen and (tribe of) Rabie.