TABARANI 4748:
from Muḥammad b. Jaʿfar b. ʿAbdullāh b. al-Zubayr —
[Machine] "The Prophet ﷺ used to dictate letters to Abdullah bin Arqam, who would then write them to the kings. One time, Abdullah informed the Prophet ﷺ that he used to write letters to some kings, and then the Prophet ﷺ would instruct him to seal them without reading them, trusting his honesty. The Prophet ﷺ also dictated letters to Zaid bin Thabit, who would write down revelations and letters to the kings as well. In their absence, if there was a need to write to some commanders of armies or kings, they would write a letter that would be read and acted upon by anyone present. Omar bin Khattab, Uthman bin Affan, Ali bin Abi Talib, Zaid bin Thabit, Mugheerah bin Shu'bah, Muawiyah bin Abi Sufyan, Khalid bin Saeed bin Al-Aas, and others from among the Arabs have all written letters on his behalf."
الطبراني ٤٧٤٨:
عن محمد بن جعفر بن عبد الله بن الزبير —
«أَنَّ النَّبِيَّ ﷺ اسْتَكْتَبَ عَبْدَ اللهِ بْنَ الْأَرْقَمِ فَكَانَ يَكْتُبُ إِلَى الْمُلُوكِ فَبَلَغَ مِنْ أَمَانَتِهِ عَنْدَهُ أَنَّهُ كَانَ يَكْتُبُ إِلَى بَعْضِ الْمُلُوكِ فَيَكْتُبُ ثُمَّ يَأْمُرُهُ أَنْ يُطَبِّقَهُ ثُمَّ يَخْتِمُ لَا يَقْرَأُهُ لِأَمانِتِهِ عَنْدَهُ واسْتَكْتَبَ أَيْضًا زَيْدَ بْنَ ثَابِتٍ فَكَانَ يَكْتُبُ الْوَحْيَ وَيَكْتُبُ إِلَى الْمُلُوكِ أَيْضًا وَكَانَ إِذَا غَابَ عَبْدُ اللهِ بْنُ الْأَرْقَمِ وَزَيْدُ بْنُ ثَابِتٍ فَاحْتَاجَ أَنْ يَكْتُبَ إِلَى بَعْضِ أُمَرَاءِ الْأَجْنَادِ وَالْمُلُوكِ وَيَكْتُبَ لِإِنْسَانٍ كِتَابًا يَقْطَعُهُ أَمَرَ مَنْ حَضَرَ أَنْ يَكْتُبَ وَقَدْ كَتَبَ لَهُ عُمَرُ بْنُ الْخَطَّابِ وَعُثْمَانُ بْنُ عَفَّانَ وَعَلِيُّ بْنُ أَبِي طَالِبٍ وَزَيْدُ بْنُ ثَابِتٍ وَالْمُغِيرَةُ بْنُ شُعْبَةَ وَمُعَاوِيَةُ بْنُ أَبِي سُفْيَانَ وَخَالِدُ بْنُ سَعِيدِ بْنِ الْعَاصِّ ؓ وَغَيْرُهُمْ مِمَّنْ قَدْ سُمَيَّ مِنَ الْعَرَبِ»
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