'Umar ibn 'Abdu'l-'Aziz asked Abu Bakr ibn Abi Hathama, "Why did Abu Bakr write, 'From Abu Bakr, the Khalifa (Successor) of the Messenger of Allah' and then 'Umar wrote after him, 'From 'Umar ibn al-Khattab, the khalifa (successor) of Abu Bakr'? Who was the first to write 'the Amir al-Mu'minin'?" He replied, "My grandmother, ash-Shifa', related to me, and she was one of the first to write 'the Amir al-Mu'minin'?" He said, "My grandfather, ash-Shifa' related to me, (and she was one of the first Muhajirun and when 'Umar ibn al-Khattab entered the market, he visited her), saying, ''Umar ibn al-Khattab wrote to the governor of Iraq requesting him to send him two trustworthy noble men so that he could question them about Iraq and its people. He sent him a master of Iraq, Labid ibn Rabi'a and also 'Adi ibn Hatim, and they came to Madina. They made their camels kneel in the courtyard of the mosque, entered it and found 'Amr ibn al-'As. They said to him, ''Amr, ask permission for us to visit the Amir al-Mu'minin, 'Umar.' 'Amr got up and went to 'Umar. He said, 'Peace be upon you, Amir al-Mu'minin.' 'Umar said to him, 'Ibn al-'As, what made you use this name? You have deviated from what you normally say.' He said, 'Yes, Labid ibn Rabi'a and 'Adi ibn Hatim came and said to me, "Ask permission for us to visit the Amir al-Mu'minin." I said, "You two, by Allah, have hit upon the correct name. He is the amir and we are the believers."' The title originated on that day."  

أَنَّ عُمَرَ بْنَ عَبْدِ الْعَزِيزِ سَأَلَ أَبَا بَكْرِ بْنَ سُلَيْمَانَ بْنِ أَبِي حَثْمَةَ لِمَ كَانَ أَبُو بَكْرٍ يَكْتُبُ مِنْ أَبِي بَكْرٍ خَلِيفَةِ رَسُولِ اللهِ ثُمَّ كَانَ عُمَرُ يَكْتُبُ بَعْدَهُ مِنْ عُمَرَ بْنِ الْخَطَّابِ خَلِيفَةِ أَبِي بَكْرٍ مَنْ أَوَّلُ مَنْ كَتَبَ أَمِيرَ الْمُؤْمِنِينَ؟ فَقَالَ حَدَّثَتْنِي جَدَّتِي الشِّفَاءُ وَكَانَتْ مِنَ الْمُهَاجِرَاتِ الأُوَلِ وَكَانَ عُمَرُ بْنُ الْخَطَّابِ رَضِيَ اللَّهُ عَنْهُ إِذَا هُوَ دَخَلَ السُّوقَ دَخَلَ عَلَيْهَا قَالَتْ كَتَبَ عُمَرُ بْنُ الْخَطَّابِ إِلَى عَامِلِ الْعِرَاقَيْنِ أَنِ ابْعَثْ إِلَيَّ بِرَجُلَيْنِ جَلْدَيْنِ نَبِيلَيْنِ أَسْأَلُهُمَا عَنِ الْعِرَاقِ وَأَهْلِهِ فَبَعَثَ إِلَيْهِ صَاحِبُ الْعِرَاقَيْنِ بِلَبِيدِ بْنِ رَبِيعَةَ وَعَدِيِّ بْنِ حَاتِمٍ فَقَدِمَا الْمَدِينَةَ فَأَنَاخَا رَاحِلَتَيْهِمَا بِفِنَاءِ الْمَسْجِدِ ثُمَّ دَخَلاَ الْمَسْجِدَ فَوَجَدَا عَمْرَو بْنَ الْعَاصِ فَقَالاَ لَهُ يَا عَمْرُو اسْتَأْذِنْ لَنَا عَلَى أَمِيرِ الْمُؤْمِنِينَ عُمَرَ فَوَثَبَ عَمْرٌو فَدَخَلَ عَلَى عُمَرَ فَقَالَ السَّلاَمُ عَلَيْكَ يَا أَمِيرَ الْمُؤْمِنِينَ فَقَالَ لَهُ عُمَرُ مَا بَدَا لَكَ فِي هَذَا الِاسْمِ يَا ابْنَ الْعَاصِ؟ لَتَخْرُجَنَّ مِمَّا قُلْتَ قَالَ نَعَمْ قَدِمَ لَبِيدُ بْنُ رَبِيعَةَ وَعَدِيُّ بْنُ حَاتِمٍ فَقَالاَ لِي اسْتَأْذِنْ لَنَا عَلَى أَمِيرِ الْمُؤْمِنِينَ فَقُلْتُ أَنْتُمَا وَاللَّهِ أَصَبْتُمَا اسْمَهُ وَإِنَّهُ الأَمِيرُ وَنَحْنُ الْمُؤْمِنُونَ فَجَرَى الْكِتَابُ مِنْ ذَلِكَ الْيَوْمِ