Banu Isra'il were ruled over by the Prophets. When one Prophet died, another succeeded him; but after me there is no prophet and there will be caliphs and they will be quite large in number. His Companions said: What do you order us to do (in case we come to have more than one Caliph)? He said: The one to whom allegiance is sworn first has a supremacy over the others. Concede to them their due rights (i. e. obey them). God (Himself) will question them about the subjects whom He had entrusted to them. (Using translation from Muslim 1842a)
قَاعَدْتُ أَبَا هُرَيْرَةَ خَمْسَ سِنِينَ فَسَمِعْتُهُ يُحَدِّثُ عَنِ النَّبِيِّ ﷺ أَنَّهُ قَالَ إِنَّ بَنِي إِسْرَائِيلَ كَانَتْ تَسُوسُهُمُ الْأَنْبِيَاءُ كُلَّمَا هَلَكَ نَبِيٌّ خَلَفَ نَبِيٌّ وَإِنَّهُ لَا نَبِيَّ بَعْدِي إِنَّهُ سَيَكُونُ خُلَفَاءُ فَتَكْثُرُ قَالُوا فَمَا تَأْمُرُنَا؟ قَالَ فُوا بِبَيْعَةِ الْأَوَّلِ فَالْأَوَّلِ وَأَعْطُوهُمْ حَقَّهُمُ الَّذِي جَعَلَ اللهُ لَهُمْ فَإِنَّ اللهَ سَائِلُهُمْ عَمَّا اسْتَرْعَاهُمْ