The Prophet felt the effects of poison.
Aisha narrates that she poured medicine into the Prophet's mouth, against his wishes.

Reference: Sahih al-Bukhari 4458

Sahih al-Bukhari 4458
Narrated `Aisha:

We poured medicine in one side of the Prophet's mouth during his illness and he started pointing to us, meaning to say, "Don't pour medicine in my mouth." We said, "(He says so) because a patient dislikes medicines." When he improved and felt a little better, he said, "Didn't I forbid you to pour medicine in my mouth ?" We said, " (We thought it was because of) the dislike, patients have for medicines. He said, "Let everyone present in the house be given medicine by pouring it in his mouth while I am looking at him, except `Abbas as he has not witnessed you (doing the same to me).

حَدَّثَنَا عَلِيٌّ، حَدَّثَنَا يَحْيَى، وَزَادَ، قَالَتْ عَائِشَةُ لَدَدْنَاهُ فِي مَرَضِهِ فَجَعَلَ يُشِيرُ إِلَيْنَا أَنْ لاَ تَلُدُّونِي فَقُلْنَا كَرَاهِيَةُ الْمَرِيضِ لِلدَّوَاءِ‏.‏ فَلَمَّا أَفَاقَ قَالَ ‏"‏ أَلَمْ أَنْهَكُمْ أَنْ تَلُدُّونِي ‏"‏‏.‏ قُلْنَا كَرَاهِيَةَ الْمَرِيضِ لِلدَّوَاءِ‏.‏ فَقَالَ ‏"‏ لاَ يَبْقَى أَحَدٌ فِي الْبَيْتِ إِلاَّ لُدَّ ـ وَأَنَا أَنْظُرُ ـ إِلاَّ الْعَبَّاسَ، فَإِنَّهُ لَمْ يَشْهَدْكُمْ ‏"‏‏.‏ رَوَاهُ ابْنُ أَبِي الزِّنَادِ عَنْ هِشَامٍ عَنْ أَبِيهِ عَنْ عَائِشَةَ عَنِ النَّبِيِّ صلى الله عليه وسلم‏.‏
Reference  : Sahih al-Bukhari 4458
In-book reference  : Book 64, Hadith 474

Note: 1. "On one side" indicates the Prophet (ﷺ) was laying down, likely sleeping when this event occured.

2. By forcing the househould who witnessed this event, to drink medicine, suggests that he was extremely suspicious of those in his household.

3. The events are dictated by A'isha, who poured the medicine. Of all the witnesses, this is the only account provided.

 
Rasullulah (ﷺ) felt as though his aorta was being cut from poison

Reference: Sahih al-Bukhari 4428

Sahih al-Bukhari 4428
Narrated `Aisha:

The Prophet (ﷺ) in his ailment in which he died, used to say, "O `Aisha! I still feel the pain caused by the food I ate at Khaibar, and at this time, I feel as if my aorta is being cut from that poison."

وَقَالَ يُونُسُ عَنِ الزُّهْرِيِّ، قَالَ عُرْوَةُ قَالَتْ عَائِشَةُ ـ رضى الله عنها ـ كَانَ النَّبِيُّ صلى الله عليه وسلم يَقُولُ فِي مَرَضِهِ الَّذِي مَاتَ فِيهِ ‏ "‏ يَا عَائِشَةُ مَا أَزَالُ أَجِدُ أَلَمَ الطَّعَامِ الَّذِي أَكَلْتُ بِخَيْبَرَ، فَهَذَا أَوَانُ وَجَدْتُ انْقِطَاعَ أَبْهَرِي مِنْ ذَلِكَ السَّمِّ ‏"‏‏.‏
Reference  : Sahih al-Bukhari 4428
In-book reference  : Book 64, Hadith 450
Note: A'isha narrates this statement.
The Calamity of the Thursday
 
On the Prophet's (ﷺ) deathbed, Umar denies the Prophet (ﷺ) paper to write "that after which you will not go astray"

Reference: Sahih al-Bukhari 5669

Sahih al-Bukhari 5669
Narrated Ibn `Abbas:

When Allah's Messenger (ﷺ) was on his death-bed and in the house there were some people among whom was `Umar bin Al-Khattab, the Prophet (ﷺ) said, "Come, let me write for you a statement after which you will not go astray." `Umar said, "The Prophet (ﷺ) is seriously ill and you have the Qur'an; so the Book of Allah is enough for us." The people present in the house differed and quarrelled. Some said "Go near so that the Prophet (ﷺ) may write for you a statement after which you will not go astray," while the others said as `Umar said. When they caused a hue and cry before the Prophet, Allah's Messenger (ﷺ) said, "Go away!" Narrated 'Ubaidullah: Ibn `Abbas used to say, "It was very unfortunate that Allah's Messenger (ﷺ) was prevented from writing that statement for them because of their disagreement and noise."

حَدَّثَنَا إِبْرَاهِيمُ بْنُ مُوسَى، حَدَّثَنَا هِشَامٌ، عَنْ مَعْمَرٍ، وَحَدَّثَنِي عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ لَمَّا حُضِرَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَفِي الْبَيْتِ رِجَالٌ فِيهِمْ عُمَرُ بْنُ الْخَطَّابِ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ هَلُمَّ أَكْتُبْ لَكُمْ كِتَابًا لاَ تَضِلُّوا بَعْدَهُ ‏"‏‏.‏ فَقَالَ عُمَرُ إِنَّ النَّبِيَّ صلى الله عليه وسلم قَدْ غَلَبَ عَلَيْهِ الْوَجَعُ وَعِنْدَكُمُ الْقُرْآنُ، حَسْبُنَا كِتَابُ اللَّهِ فَاخْتَلَفَ أَهْلُ الْبَيْتِ فَاخْتَصَمُوا، مِنْهُمْ مَنْ يَقُولُ قَرِّبُوا يَكْتُبْ لَكُمُ النَّبِيُّ صلى الله عليه وسلم كِتَابًا لَنْ تَضِلُّوا بَعْدَهُ، وَمِنْهُمْ مَنْ يَقُولُ مَا قَالَ عُمَرُ فَلَمَّا أَكْثَرُوا اللَّغْوَ وَالاِخْتِلاَفَ عِنْدَ النَّبِيِّ صلى الله عليه وسلم قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ قُومُوا ‏"‏‏.‏ قَالَ عُبَيْدُ اللَّهِ فَكَانَ ابْنُ عَبَّاسٍ يَقُولُ إِنَّ الرَّزِيَّةَ كُلَّ الرَّزِيَّةِ مَا حَالَ بَيْنَ رَسُولِ اللَّهِ صلى الله عليه وسلم وَبَيْنَ أَنْ يَكْتُبَ لَهُمْ ذَلِكَ الْكِتَابَ مِنِ اخْتِلاَفِهِمْ وَلَغَطِهِمْ‏.‏‏‏
Reference  : Sahih al-Bukhari 5669
In-book reference  : Book 75, Hadith 29
 
A'isha states that while the Rasulullah was on his death bed, he stated three times about the Highest Companion. Umar then frightened the people. A'isha testifies that some surrounding the Prophet were hypocrites who abandoned Islam because of Umar's speech.
Sahih al-Bukhari 3669, 3670
Aisha said (in another narration):

When the Prophet (ﷺ) was on his death-bed) he looked up and said thrice: the Highest Companion (See Qur'an 4:69)' Aisha said, Allah benefited the people by their two speeches. 'Umar frightened the people some of whom were hypocrites whom Allah caused to abandon Islam because of 'Umar's speech. Then Abu Bakr led the people to True Guidance and acquainted them with the right path4 they were to follow so that they went out reciting: "Muhammad is no more than an Apostle and indeed many Apostles have passed away before him.." (3.144)

وَقَالَ عَبْدُ اللَّهِ بْنُ سَالِمٍ عَنِ الزُّبَيْدِيِّ، قَالَ عَبْدُ الرَّحْمَنِ بْنُ الْقَاسِمِ أَخْبَرَنِي الْقَاسِمُ، أَنَّ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ شَخَصَ بَصَرُ النَّبِيِّ صلى الله عليه وسلم ثُمَّ قَالَ ‏"‏ فِي الرَّفِيقِ الأَعْلَى ‏"‏‏.‏ ثَلاَثًا، وَقَصَّ الْحَدِيثَ، قَالَتْ فَمَا كَانَتْ مِنْ خُطْبَتِهِمَا مِنْ خُطْبَةٍ إِلاَّ نَفَعَ اللَّهُ بِهَا، لَقَدْ خَوَّفَ عُمَرُ النَّاسَ وَإِنَّ فِيهِمْ لَنِفَاقًا، فَرَدَّهُمُ اللَّهُ بِذَلِكَ‏.‏ ثُمَّ لَقَدْ بَصَّرَ أَبُو بَكْرٍ النَّاسَ الْهُدَى وَعَرَّفَهُمُ الْحَقَّ الَّذِي عَلَيْهِمْ وَخَرَجُوا بِهِ يَتْلُونَ ‏{‏وَمَا مُحَمَّدٌ إِلاَّ رَسُولٌ قَدْ خَلَتْ مِنْ قَبْلِهِ الرُّسُلُ‏}‏ إِلَى ‏{‏الشَّاكِرِينَ‏}‏
Reference  : Sahih al-Bukhari 3669, 3670
In-book reference  : Book 62, Hadith 20

Note: 1. An interpretation of this hadith is that Umar's speech (or public disobediance of the Prophet's command) gave those around the deathbed the courage to also abandon the Prophet's command.

2. The Quran verse 4:69 is a later insertion and interpretation of this Hadith. Some argue this provides evidence that the Prophet intended to remind the companions of his command at Ghadeer - his successor and therefore the highest companion.

3. An interpretation that relates to Quran 4:69 does not distinguish one companion from another. It is simply an instruction to Obey Allah (swt) and his Messenger (ﷺ). Hence, this is not an appropriate interpretation of how one determines who the Highest Companion is.

4. A'isha will of course claim her father led the people to the "True Guidance" and the right path, hence such a statement can be discarded as strictly her biased opinion.

The Prophet (ﷺ) in a state of extreme sickness, unable to get up. Yet, the Prophet is carried to lead the prayer.
 
In extreme sickness, a messenger is sent to instruct Abu Bakr to lead the prayer, while the Prophet is in an unconscious state. A'isha claims the Prophet sent the messenger.

Reference: Sahih Muslim 418a

Sahih Muslim 418a
Ubaidullah b. Abdullah reported:

I visited 'A'isha and asked her to tell about the illness of the Messenger of Allah (ﷺ). She agreed and said:1 The Apostle (ﷺ) was seriously ill and he asked whether the people had prayed. We said: No, they are waiting for you, Messenger of Allah. He (the Holy Prophet) said: Put some water in the tub for me. We did accordingly and he (the Holy Prophet) took a bath; and, when he was about to move with difficulty, he fainted. When he came round, he again said: Have the people said prayer? We said: No, they are waiting for you, Messenger of Allah. He (the Holy Prophet) again said: Put some water for me in the tub. We did accordingly and he took a bag, but when he was about to move with difficulty he fainted. When he came round, he asked whether the people had prayed. We said: No, they are waiting for you, Messenger of Allah. He said: Put some water for me in the tub. We did accordingly and he took a bath and he was about to move with difficulty when he fainted. When he came round he said: Have the people said prayer? We said: No, they are waiting for you, Messenger of Allah. She ('A'isha) said: The people were staying in the mosque and waiting for the Messenger of Allah (ﷺ) to lead the last (night) prayer. She ('A'isha) said: The Messenger of Allah (ﷺ) sent (instructions) to Abu Bakr to lead the people in prayer. When the messenger came,2 he told him (Abu Bakr): The Messenger of Allah (ﷺ) has ordered you to lead the people in prayer. Abu Bakr who was a man of very tenderly feelings asked Umar to lead the prayer. 'Umar said: You are more entitled to that. Abu Bakr led the prayers during those days. Afterwards the Messenger of Allah (ﷺ) felt some relief and he went out supported by two men, one of them was al-'Abbas, to the noon prayer.3 Abu Bakr was leading the people in prayer. When Abu Bakr saw him. he began to withdraw, but the Messenger of Allah (ﷺ) told him not to withdraw. He told his two (companions) to seat him down beside him (Abu Bakr). They seated him by the side of Abu Bakr. Abu Bakr said the prayer standing while following the prayer of the Apostle (ﷺ)4 and the people prayed the prayer of Abu Bakr (standing)5 and the Apostle (ﷺ) while seated. Ubaidullah said: I visited 'Abdullah b. 'Abbas, and said: Should I submit to you what 'A'isha had told about the illness of the Apostle (ﷺ)?6 He said: Go ahead. I submitted to him what had been transmitted by her ('A'isha). He objected to none of it, only asking whether she had named to him the man who accompanied al-'Abbas. I said: No. He said: It was 'Ali.

> حَدَّثَنَا أَحْمَدُ بْنُ عَبْدِ اللَّهِ بْنِ يُونُسَ، حَدَّثَنَا زَائِدَةُ، حَدَّثَنَا مُوسَى بْنُ أَبِي عَائِشَةَ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، قَالَ دَخَلْتُ عَلَى عَائِشَةَ فَقُلْتُ لَهَا أَلاَ تُحَدِّثِينِي عَنْ مَرَضِ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَتْ بَلَى ثَقُلَ النَّبِيُّ صلى الله عليه وسلم فَقَالَ ‏"‏ أَصَلَّى النَّاسُ ‏"‏ ‏.‏ قُلْنَا لاَ وَهُمْ يَنْتَظِرُونَكَ يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ ضَعُوا لِي مَاءً فِي الْمِخْضَبِ ‏"‏ ‏.‏ فَفَعَلْنَا فَاغْتَسَلَ ثُمَّ ذَهَبَ لِيَنُوءَ فَأُغْمِيَ عَلَيْهِ ثُمَّ أَفَاقَ فَقَالَ ‏"‏ أَصَلَّى النَّاسُ ‏"‏ ‏.‏ قُلْنَا لاَ وَهُمْ يَنْتَظِرُونَكَ يَا رَسُولَ اللَّهِ ‏.‏ فَقَالَ ‏"‏ ضَعُوا لِي مَاءً فِي الْمِخْضَبِ ‏"‏ ‏.‏ فَفَعَلْنَا فَاغْتَسَلَ ثُمَّ ذَهَبَ لِيَنُوءَ فَأُغْمِيَ عَلَيْهِ ثُمَّ أَفَاقَ فَقَالَ ‏"‏ أَصَلَّى النَّاسُ ‏"‏ ‏.‏ قُلْنَا لاَ وَهُمْ يَنْتَظِرُونَكَ يَا رَسُولَ اللَّهِ ‏.‏ فَقَالَ ‏"‏ ضَعُوا لِي مَاءً فِي الْمِخْضَبِ ‏"‏ ‏.‏ فَفَعَلْنَا فَاغْتَسَلَ ثُمَّ ذَهَبَ لِيَنُوءَ فَأُغْمِيَ عَلَيْهِ ثُمَّ أَفَاقَ فَقَالَ ‏"‏ أَصَلَّى النَّاسُ ‏"‏ ‏.‏ فَقُلْنَا لاَ وَهُمْ يَنْتَظِرُونَكَ يَا رَسُولَ اللَّهِ ‏.‏ قَالَتْ وَالنَّاسُ عُكُوفٌ فِي الْمَسْجِدِ يَنْتَظِرُونَ رَسُولَ اللَّهِ صلى الله عليه وسلم لِصَلاَةِ الْعِشَاءِ الآخِرَةِ - قَالَتْ - فَأَرْسَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِلَى أَبِي بَكْرٍ أَنْ يُصَلِّيَ بِالنَّاسِ فَأَتَاهُ الرَّسُولُ فَقَالَ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم يَأْمُرُكَ أَنْ تُصَلِّيَ بِالنَّاسِ ‏.‏ فَقَالَ أَبُو بَكْرٍ وَكَانَ رَجُلاً رَقِيقًا يَا عُمَرُ صَلِّ بِالنَّاسِ ‏.‏ قَالَ فَقَالَ عُمَرُ أَنْتَ أَحَقُّ بِذَلِكَ ‏.‏ قَالَتْ فَصَلَّى بِهِمْ أَبُو بَكْرٍ تِلْكَ الأَيَّامَ ثُمَّ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم وَجَدَ مِنْ نَفْسِهِ خِفَّةً فَخَرَجَ بَيْنَ رَجُلَيْنِ أَحَدُهُمَا الْعَبَّاسُ لِصَلاَةِ الظُّهْرِ وَأَبُو بَكْرٍ يُصَلِّي بِالنَّاسِ فَلَمَّا رَآهُ أَبُو بَكْرٍ ذَهَبَ لِيَتَأَخَّرَ فَأَوْمَأَ إِلَيْهِ النَّبِيُّ صلى الله عليه وسلم أَنْ لاَ يَتَأَخَّرَ وَقَالَ لَهُمَا ‏"‏ أَجْلِسَانِي إِلَى جَنْبِهِ ‏"‏ ‏.‏ فَأَجْلَسَاهُ إِلَى جَنْبِ أَبِي بَكْرٍ وَكَانَ أَبُو بَكْرٍ يُصَلِّي وَهُوَ قَائِمٌ بِصَلاَةِ النَّبِيِّ صلى الله عليه وسلم وَالنَّاسُ يُصَلُّونَ بِصَلاَةِ أَبِي بَكْرٍ وَالنَّبِيُّ صلى الله عليه وسلم قَاعِدٌ ‏.‏ قَالَ عُبَيْدُ اللَّهِ فَدَخَلْتُ عَلَى عَبْدِ اللَّهِ بْنِ عَبَّاسٍ فَقُلْتُ لَهُ أَلاَ أَعْرِضُ عَلَيْكَ مَا حَدَّثَتْنِي عَائِشَةُ عَنْ مَرَضِ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ هَاتِ ‏.‏ فَعَرَضْتُ حَدِيثَهَا عَلَيْهِ فَمَا أَنْكَرَ مِنْهُ شِيْئًا غَيْرَ أَنَّهُ قَالَ أَسَمَّتْ لَكَ الرَّجُلَ الَّذِي كَانَ مَعَ الْعَبَّاسِ قُلْتُ لاَ ‏.‏ قَالَ هُوَ عَلِيٌّ ‏.‏
Reference  : Sahih Muslim 418a
In-book reference  : Book 4, Hadith 98

Note: 1. This actual narrator of this hadith is in fact Aisha, not Ubaidullah Ibn `Abdullah bin `Utba.

2. A'isha claims the Prophet sent a messenger to instruct Abu Bakr to lead the prayer, but this cannot be verified independently. Given the implication, and how this claim is used today to legitimize Abu Bakr, this must be treated with a great deal of skepiticism especially when the only narrator of such an important claim is the daughter of the beneficiary of the claim.

3. The Prophet in his extreme sickness is carried to lead the prayers after he regains consciousness.

4. Abu Bakr followed the Prophet in prayer, he did not lead the prayer. Abu Bakr only led the prayer while the Prophet was in an unconscious state, under an instruction from a messenger that cannot be independently verified as having originated from the Prophet himself.

5. The people prayed the prayer of Abu Bakr, meaning a standing prayer, they did not follow Abu Bakr in prayer, a key distinction. To claim the people followed Abu Bakr in prayer is a misrepresentation of the Arabic text. This is validated by Bukhari 713 below.

6. Ibn Abbas did not object to the statements regarding the "illness" of the Prophet, but this does not ratify A'isha's claim that the Prophet sent the messenger.

 
The Prophet is so sick that he needs to be carried out of the house of A'isha, with his feet dragging on the ground. He is carried by Abbas and Ali.

Reference: Sahih Muslim 418c

Sahih Muslim 418c
'A'isha, the wife of the Apostle (ﷺ), said:

When the Messenger of Allah (ﷺ) fell ill and his illness became serious, he asked permission from his wives to stay in my house during his illness. They gave him permission to do so. He stepped out (of'A'isha's apartment for prayer) supported by two persons. (He was so much weak) that his feet dragged on the ground and he was being supported by 'Abbas b. 'Abd al-Muttalib and another person. 'Ubaidullah said: I informed 'Abdullah (b. 'Abbas) about that which 'A'isha had said. 'Abdullah b. 'Abbas said: Do you know the man whose name 'A'isha did not mention? He said: No. Ibn 'Abbas said: It was 'Ali.

حَدَّثَنِي عَبْدُ الْمَلِكِ بْنُ شُعَيْبِ بْنِ اللَّيْثِ، حَدَّثَنِي أَبِي، عَنْ جَدِّي، قَالَ حَدَّثَنِي عُقَيْلُ بْنُ خَالِدٍ، قَالَ ابْنُ شِهَابٍ أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ بْنِ مَسْعُودٍ، أَنَّ عَائِشَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم قَالَتْ لَمَّا ثَقُلَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَاشْتَدَّ بِهِ وَجَعُهُ اسْتَأْذَنَ أَزْوَاجَهُ أَنْ يُمَرَّضَ فِي بَيْتِي فَأَذِنَّ لَهُ فَخَرَجَ بَيْنَ رَجُلَيْنِ تَخُطُّ رِجْلاَهُ فِي الأَرْضِ بَيْنَ عَبَّاسِ بْنِ عَبْدِ الْمُطَّلِبِ وَبَيْنَ رَجُلٍ آخَرَ ‏.‏ قَالَ عُبَيْدُ اللَّهِ فَأَخْبَرْتُ عَبْدَ اللَّهِ بِالَّذِي قَالَتْ عَائِشَةُ فَقَالَ لِي عَبْدُ اللَّهِ بْنُ عَبَّاسٍ هَلْ تَدْرِي مَنِ الرَّجُلُ الآخَرُ الَّذِي لَمْ تُسَمِّ عَائِشَةُ قَالَ قُلْتُ لاَ ‏.‏ قَالَ ابْنُ عَبَّاسٍ هُوَ عَلِيٌّ ‏.
Reference  : Sahih Muslim 418c
In-book reference  : Book 4, Hadith 100
 
In the Prophet's sick state, he refuses to allow Abu Bakr to lead the prayer.

Reference: Sahih al-Bukhari 713

Sahih al-Bukhari 713
'Narrated `Aisha:

When Allah's Messenger (ﷺ) became seriously ill, Bilal came to him for the prayer. He said, "Tell Abu Bakr to lead the people in the prayer." I said, "O Allah's Messenger (ﷺ)! Abu Bakr is a softhearted man and if he stands in your place, he would not be able to make the people hear him. Will you order `Umar (to lead the prayer)?" The Prophet (ﷺ) said, "Tell Abu Bakr to lead the people in the prayer." Then I said to Hafsa, "Tell him, Abu Bakr is a softhearted man and if he stands in his place, he would not be able to make the people hear him. Would you order `Umar to lead the prayer?' " Hafsa did so. The Prophet (ﷺ) said, "Verily you are the companions of Joseph.1 Tell Abu Bakr to lead the people in the prayer." So Abu Bakr stood for the prayer. In the meantime Allah's Messenger (ﷺ) felt better and came out with the help of two persons and both of his legs were dragging on the ground till he entered the mosque.2 When Abu Bakr heard him coming, he tried to retreat but Allah's Messenger (ﷺ) beckoned him to carry on. The Prophet (ﷺ) sat on his left side. Abu Bakr was praying while standing and Allah's Messenger (ﷺ) was leading the prayer while sitting. Abu Bakr was following the Prophet (ﷺ)3 and the people were immitating Abu Bakr (in the prayer).4

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتْ لَمَّا ثَقُلَ رَسُولُ اللَّهِ صلى الله عليه وسلم جَاءَ بِلاَلٌ يُؤْذِنُهُ بِالصَّلاَةِ فَقَالَ ‏"‏ مُرُوا أَبَا بَكْرٍ أَنْ يُصَلِّيَ بِالنَّاسِ ‏"‏‏.‏ فَقُلْتُ يَا رَسُولَ اللَّهِ، إِنَّ أَبَا بَكْرٍ رَجُلٌ أَسِيفٌ، وَإِنَّهُ مَتَى مَا يَقُمْ مَقَامَكَ لاَ يُسْمِعُ النَّاسَ، فَلَوْ أَمَرْتَ عُمَرَ‏.‏ فَقَالَ ‏"‏ مُرُوا أَبَا بَكْرٍ يُصَلِّي بِالنَّاسِ ‏"‏‏.‏ فَقُلْتُ لِحَفْصَةَ قُولِي لَهُ إِنَّ أَبَا بَكْرٍ رَجُلٌ أَسِيفٌ، وَإِنَّهُ مَتَى يَقُمْ مَقَامَكَ لاَ يُسْمِعِ النَّاسَ، فَلَوْ أَمَرْتَ عُمَرَ‏.‏ قَالَ ‏"‏ إِنَّكُنَّ لأَنْتُنَّ صَوَاحِبُ يُوسُفَ، مُرُوا أَبَا بَكْرٍ أَنْ يُصَلِّيَ بِالنَّاسِ ‏"‏‏.‏ فَلَمَّا دَخَلَ فِي الصَّلاَةِ وَجَدَ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي نَفْسِهِ خِفَّةً، فَقَامَ يُهَادَى بَيْنَ رَجُلَيْنِ، وَرِجْلاَهُ يَخُطَّانِ فِي الأَرْضِ حَتَّى دَخَلَ الْمَسْجِدَ، فَلَمَّا سَمِعَ أَبُو بَكْرٍ حِسَّهُ ذَهَبَ أَبُو بَكْرٍ يَتَأَخَّرُ، فَأَوْمَأَ إِلَيْهِ رَسُولُ اللَّهِ صلى الله عليه وسلم، فَجَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم حَتَّى جَلَسَ عَنْ يَسَارِ أَبِي بَكْرٍ، فَكَانَ أَبُو بَكْرٍ يُصَلِّي قَائِمًا، وَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي قَاعِدًا، يَقْتَدِي أَبُو بَكْرٍ بِصَلاَةِ رَسُولِ اللَّهِ صلى الله عليه وسلم وَالنَّاسُ مُقْتَدُونَ بِصَلاَةِ أَبِي بَكْرٍ رضى الله عنه‏.‏
Reference  : Sahih al-Bukhari 713
In-book reference  : Book 10, Hadith 108

Note: This hadith is narrated by A'isha, the daughter of the Abu Bakr. She has an incentive to narrate such a hadith in favour of her father.

1. The Prophet compares A'isha and Hafsa to the trecherous brothers of Yusuf, while in his dying state. Hence, her narrations are dubious and likely narrated for self interest purposes.

2. The Prophet is so sick, he cannot walk without being carried, yet he is unwilling to let Abu Bakr lead the prayer without him.

3. The claim that Abu Bakr led the prayer is disproved by A'isha own words, wherein she states that Abu Bakr followed the Prophet. The word yaqtadi means lead by, as in Abu Bakr was led by the Prophet sws. In his sickly state, the Prophet did not allow Abu Bakr to lead independently.

4. The word muqtadoon means immitating, not following. Hence, they immitated Abu Bakr, but followed or were lead by the Prophet sws.

After the prayer, Rasullulah (ﷺ) orders all Muslims (except Ali) to leave Mecca and join the army of Usama. His order is not obeyed.
 
The Prophet in his ailment, after the prayer, orders his companions to join the army of Usama bin Zaid.

Reference: Sahih al-Bukhari 5714

Sahih al-Bukhari 198
Narrated `Aisha:

(the wife of the Prophet) When the health of Allah's Messenger (ﷺ) deteriorated and his condition became serious, he asked the permission of all his wives to allow him to be treated In my house, and they allowed him. He came out, supported by two men and his legs were dragging on the ground between `Abbas and another man. (The sub-narrator told Ibn `Abbas who said: Do you know who was the other man whom `Aisha did not mention? The sub-narrator said: No. Ibn `Abbas said: It was `Ali.) `Aisha added: When the Prophet entered my house and his disease became aggravated, he said, "Pour on me seven water skins full of water (the tying ribbons of which had not been untied) so that I may give some advice to the people." So we made him sit in a tub belonging to Hafsa, the wife of the Prophet (ﷺ) and started pouring water on him from those water skins till he waved us to stop. Then he went out to the people and led them in prayer and delivered a speech before them.

حَدَّثَنَا أَبُو الْيَمَانِ، قَالَ أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّ عَائِشَةَ، قَالَتْ لَمَّا ثَقُلَ النَّبِيُّ صلى الله عليه وسلم وَاشْتَدَّ بِهِ وَجَعُهُ، اسْتَأْذَنَ أَزْوَاجَهُ فِي أَنْ يُمَرَّضَ فِي بَيْتِي، فَأَذِنَّ لَهُ، فَخَرَجَ النَّبِيُّ صلى الله عليه وسلم بَيْنَ رَجُلَيْنِ تَخُطُّ رِجْلاَهُ فِي الأَرْضِ بَيْنَ عَبَّاسٍ وَرَجُلٍ آخَرَ‏.‏ قَالَ عُبَيْدُ اللَّهِ فَأَخْبَرْتُ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ فَقَالَ أَتَدْرِي مَنِ الرَّجُلُ الآخَرُ قُلْتُ لاَ‏.‏ قَالَ هُوَ عَلِيٌّ‏.‏ وَكَانَتْ عَائِشَةُ ـ رضى الله عنها ـ تُحَدِّثُ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ بَعْدَ مَا دَخَلَ بَيْتَهُ وَاشْتَدَّ وَجَعُهُ ‏ "‏ هَرِيقُوا عَلَىَّ مِنْ سَبْعِ قِرَبٍ، لَمْ تُحْلَلْ أَوْكِيَتُهُنَّ، لَعَلِّي أَعْهَدُ إِلَى النَّاسِ ‏"‏‏.‏ وَأُجْلِسَ فِي مِخْضَبٍ لِحَفْصَةَ زَوْجِ النَّبِيِّ صلى الله عليه وسلم، ثُمَّ طَفِقْنَا نَصُبُّ عَلَيْهِ تِلْكَ حَتَّى طَفِقَ يُشِيرُ إِلَيْنَا أَنْ قَدْ فَعَلْتُنَّ، ثُمَّ خَرَجَ إِلَى النَّاسِ‏.
Reference  : Sahih al-Bukhari 5714
In-book reference  : Book 76, Hadith 31
 
Usama at 18 was put in charge of the army. "The people contested his leadership." and refused to leave.
Jami` at-Tirmidhi Book 49, Hadith 216
Narrated Ibn 'Umar:

that the Messenger of Allah (ﷺ) sent and army and put Usamah bin Zaid in charge of them. So the people contested his leadership, so the Prophet (ﷺ) said: 'If you contest his leadership, then you did contest the leadership of his father before him. And indeed, by Allah, he was certainly fit for leadership, and he was of the most beloved of people to me, and this one is among the most beloved of people to me after him.'"

حَدَّثَنَا أَحْمَدُ بْنُ الْحَسَنِ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، عَنْ مَالِكِ بْنِ أَنَسٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم بَعَثَ بَعْثًا وَأَمَّرَ عَلَيْهِمْ أُسَامَةَ بْنَ زَيْدٍ فَطَعَنَ النَّاسُ فِي إِمَارَتِهِ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ إِنْ تَطْعَنُوا فِي إِمَارَتِهِ فَقَدْ كُنْتُمْ تَطْعَنُونَ فِي إِمْرَةِ أَبِيهِ مِنْ قَبْلُ وَايْمُ اللَّهِ إِنْ كَانَ لَخَلِيقًا لِلإِمَارَةِ وَإِنْ كَانَ مِنْ أَحَبِّ النَّاسِ إِلَىَّ وَإِنَّ هَذَا مِنْ أَحَبِّ النَّاسِ إِلَىَّ بَعْدَهُ ‏"‏ ‏. هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ ‏.