The obligation of fulfilling oaths of allegiance is owed to the first of two Caliphs

It has been narrated by Abu Huraira that the Holy Prophet (may pceace be upon him) said: 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.

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ فُرَاتٍ الْقَزَّازِ، عَنْ أَبِي حَازِمٍ، قَالَ قَاعَدْتُ أَبَا هُرَيْرَةَ خَمْسَ سِنِينَ فَسَمِعْتُهُ يُحَدِّثُ، عَنِ النَّبِيِّ ﷺ قَالَ " كَانَتْ بَنُو إِسْرَائِيلَ تَسُوسُهُمُ الأَنْبِيَاءُ كُلَّمَا هَلَكَ نَبِيٌّ خَلَفَهُ نَبِيٌّ وَإِنَّهُ لاَ نَبِيَّ بَعْدِي وَسَتَكُونُ خُلَفَاءُ فَتَكْثُرُ " . قَالُوا فَمَا تَأْمُرُنَا قَالَ " فُوا بِبَيْعَةِ الأَوَّلِ فَالأَوَّلِ وَأَعْطُوهُمْ حَقَّهُمْ فَإِنَّ اللَّهَ سَائِلُهُمْ عَمَّا اسْتَرْعَاهُمْ " .

The same tradition has been transmitted by a different chain of narrators.

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَعَبْدُ اللَّهِ بْنُ بَرَّادٍ الأَشْعَرِيُّ، قَالاَ حَدَّثَنَا عَبْدُ اللَّهِ، بْنُ إِدْرِيسَ عَنِ الْحَسَنِ بْنِ فُرَاتٍ، عَنْ أَبِيهِ، بِهَذَا الإِسْنَادِ مِثْلَهُ .

It has been narrated on the authority of 'Abdullah who said: The Messenger of Allah ﷺ said: After me there will be favouritism anad many things that you will not like. They (his Companions) said: Messenger of Allah, what do you order that one should do it anyone from us has to live through such a time? He said: You should discharge your own responsibility (by obeying your Amir), and ask God to cuncede your right (by guiding the Amir to the right path or by replacing him by one more just and God-fearing).

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو الأَحْوَصِ، وَوَكِيعٌ، ح وَحَدَّثَنِي أَبُو سَعِيدٍ، الأَشَجُّ حَدَّثَنَا وَكِيعٌ، ح وَحَدَّثَنَا أَبُو كُرَيْبٍ، وَابْنُ، نُمَيْرٍ قَالاَ حَدَّثَنَا أَبُو مُعَاوِيَةَ، ح وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، وَعَلِيُّ بْنُ خَشْرَمٍ، قَالاَ أَخْبَرَنَا عِيسَى بْنُ يُونُسَ، كُلُّهُمْ عَنِ الأَعْمَشِ، ح وَحَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، - وَاللَّفْظُ لَهُ - حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ زَيْدِ بْنِ، وَهْبٍ عَنْ عَبْدِ اللَّهِ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " إِنَّهَا سَتَكُونُ بَعْدِي أَثَرَةٌ وَأُمُورٌ تُنْكِرُونَهَا " . قَالُوا يَا رَسُولَ اللَّهِ كَيْفَ تَأْمُرُ مَنْ أَدْرَكَ مِنَّا ذَلِكَ قَالَ " تُؤَدُّونَ الْحَقَّ الَّذِي عَلَيْكُمْ وَتَسْأَلُونَ اللَّهَ الَّذِي لَكُمْ " .

It has been narrated on the authority of 'Abd al-Rahman b. Abd Rabb al-Ka'ba who said: I entered the mosque when 'Abdullah b. 'Amr b. al-'As was sitting in the shade of the Ka'ba and the people had gathered around him. I betook myself to them and sat near him. (Now) Abdullah said: I accompanied the Messenger of Allah ﷺ on a journey. We halted at a place. Some of us began to set right their tents, others began to compete with one another in shooting, and others began to graze their beasts, when an announcer of the Messenger of Allah ﷺ announced that the people should gather together for prayer, so we gathered around the Messenger of Allah ﷺ. He said: It was the duty of every Prophet that has gone before me to guide his followers to what he knew was good for them and warn them against what he knew was bad for them;
but this Umma of yours has its days of peace and (security) in the beginning of its career, and in the last phase of its existence it will be afflicted with trials and with things disagreeable to you. (In this phase of the Umma), there will be tremendous trials one after the other, each making the previous one dwindle into insignificance. When they would be afflicted with a trial, the believer would say: This is going to bring about my destruction. When at (the trial) is over, they would be afflicted with another trial, and the believer would say: This surely is going to be my end. Whoever wishes to be delivered from the fire and enter the garden should die with faith in Allah and the Last Day and should treat the people as he wishes to be treated by them. He who swears allegiance to a Caliph should give him the piedge of his hand and the sincerity of his heart (i. e. submit to him both outwardly as well as inwardly). He should obey him to the best of his capacity. It another man comes forward (as a claimant to Caliphate), disputing his authority, they (the Muslims) should behead the latter. The narrator says: I came close to him ('Abdullah b. 'Amr b. al-'As) and said to him: Can you say on oath that you heard it from the Messenger of Allah ﷺ? He pointed with his hands to his ears and his heart and said: My ears heard it and my mind retained it. I said to him: This cousin of yours, Mu'awiya, orders us to unjustly consume our wealth among ourselves and to kill one another, while Allah says:" O ye who believe, do not consume your wealth among yourselves unjustly, unless it be trade based on mutual agreement, and do not kill yourselves. Verily, God is Merciful to you" (iv. 29). The narrator says that (hearing this) Abdullah b. 'Amr b. al-As kept quiet for a while and then said: Obey him in so far as he is obedient to God;
and diqobey him in matters involving disobedience to God.

حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ إِسْحَاقُ أَخْبَرَنَا وَقَالَ، زُهَيْرٌ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ زَيْدِ بْنِ وَهْبٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدِ رَبِّ الْكَعْبَةِ، قَالَ دَخَلْتُ الْمَسْجِدَ فَإِذَا عَبْدُ اللَّهِ بْنُ عَمْرِو بْنِ الْعَاصِ جَالِسٌ فِي ظِلِّ الْكَعْبَةِ وَالنَّاسُ مُجْتَمِعُونَ عَلَيْهِ فَأَتَيْتُهُمْ فَجَلَسْتُ إِلَيْهِ فَقَالَ كُنَّا مَعَ رَسُولِ اللَّهِ ﷺ فِي سَفَرٍ فَنَزَلْنَا مَنْزِلاً فَمِنَّا مَنْ يُصْلِحُ خِبَاءَهُ وَمِنَّا مَنْ يَنْتَضِلُ وَمِنَّا مَنْ هُوَ فِي جَشَرِهِ إِذْ نَادَى مُنَادِي رَسُولِ اللَّهِ ﷺ الصَّلاَةَ جَامِعَةً . فَاجْتَمَعْنَا إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَ " إِنَّهُ لَمْ يَكُنْ نَبِيٌّ قَبْلِي إِلاَّ كَانَ حَقًّا عَلَيْهِ أَنْ يَدُلَّ أُمَّتَهُ عَلَى خَيْرِ مَا يَعْلَمُهُ لَهُمْ وَيُنْذِرَهُمْ شَرَّ مَا يَعْلَمُهُ لَهُمْ وَإِنَّ أُمَّتَكُمْ هَذِهِ جُعِلَ عَافِيَتُهَا فِي أَوَّلِهَا وَسَيُصِيبُ آخِرَهَا بَلاَءٌ وَأُمُورٌ تُنْكِرُونَهَا وَتَجِيءُ فِتْنَةٌ فَيُرَقِّقُ بَعْضُهَا بَعْضًا وَتَجِيءُ الْفِتْنَةُ فَيَقُولُ الْمُؤْمِنُ هَذِهِ مُهْلِكَتِي . ثُمَّ تَنْكَشِفُ وَتَجِيءُ الْفِتْنَةُ فَيَقُولُ الْمُؤْمِنُ هَذِهِ هَذِهِ . فَمَنْ أَحَبَّ أَنْ يُزَحْزَحَ عَنِ النَّارِ وَيَدْخُلَ الْجَنَّةَ فَلْتَأْتِهِ مَنِيَّتُهُ وَهُوَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ وَلْيَأْتِ إِلَى النَّاسِ الَّذِي يُحِبُّ أَنْ يُؤْتَى إِلَيْهِ وَمَنْ بَايَعَ إِمَامًا فَأَعْطَاهُ صَفْقَةَ يَدِهِ وَثَمَرَةَ قَلْبِهِ فَلْيُطِعْهُ إِنِ اسْتَطَاعَ فَإِنْ جَاءَ آخَرُ يُنَازِعُهُ فَاضْرِبُوا عُنُقَ الآخَرِ " . فَدَنَوْتُ مِنْهُ فَقُلْتُ لَهُ أَنْشُدُكَ اللَّهَ آنْتَ سَمِعْتَ هَذَا مِنْ رَسُولِ اللَّهِ ﷺ فَأَهْوَى إِلَى أُذُنَيْهِ وَقَلْبِهِ بِيَدَيْهِ وَقَالَ سَمِعَتْهُ أُذُنَاىَ وَوَعَاهُ قَلْبِي . فَقُلْتُ لَهُ هَذَا ابْنُ عَمِّكَ مُعَاوِيَةُ يَأْمُرُنَا أَنْ نَأْكُلَ أَمْوَالَنَا بَيْنَنَا بِالْبَاطِلِ وَنَقْتُلَ أَنْفُسَنَا وَاللَّهُ يَقُولُ { يَا أَيُّهَا الَّذِينَ آمَنُوا لاَ تَأْكُلُوا أَمْوَالَكُمْ بَيْنَكُمْ بِالْبَاطِلِ إِلاَّ أَنْ تَكُونَ تِجَارَةً عَنْ تَرَاضٍ مِنْكُمْ وَلاَ تَقْتُلُوا أَنْفُسَكُمْ إِنَّ اللَّهَ كَانَ بِكُمْ رَحِيمًا} قَالَ فَسَكَتَ سَاعَةً ثُمَّ قَالَ أَطِعْهُ فِي طَاعَةِ اللَّهِ وَاعْصِهِ فِي مَعْصِيَةِ اللَّهِ .

This hadith has been narrated on the authority of A'mash with a different chain of transmitters.

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَابْنُ، نُمَيْرٍ وَأَبُو سَعِيدٍ الأَشَجُّ قَالُوا حَدَّثَنَا وَكِيعٌ، ح وَحَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، كِلاَهُمَا عَنِ الأَعْمَشِ، بِهَذَا الإِسْنَادِ نَحْوَهُ .