عَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جَدِّهِ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ كَتَبَ كِتَابًا بَيْنَ الْمُهَاجِرِينَ وَالْأَنْصَارِ أَنْ يَعْقِلُوا مَعَاقِلَهُمْ وَأَنْ يَفْدُوا عَانِيَهُمْ بِالْمَعْرُوفِ وَالْإِصْلَاحِ بَيْنَ الْمُسْلِمِينَ
It is narrated from Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) wrote an agreement between the Muhajirun and the Ansar that all of them would collectively pay blood money for one another, would free each other's captives in a recognized manner, and would bring about reconciliation among the Muslims.