Majority Muslims believe he died a natural death, some believe he was assassinated but dispute who did it The Quran confirms he was assassinated in the following verse.
Quran 3:144 “Muhammad is no more than a messenger: many were the messengers that passed away before him. If he died or is killed, will ye then Turn back on your heels?..”
The conjunctive (or) in this verse means “Rather”. In Arabic, sometimes (or) indicates uncertainty and probability. In other contexts, it imparts correction. Since it is next to impossible that any Muslim should suspect Allah’s word, since He has insight into the unknown, Allah must have intended to impart the other meaning. Accordingly a correct translation of the verse would be
Quran 3:144 “Muhammad is no more than a messenger: many were the messengers that passed away before him. If he died, rather, is killed, will ye then Turn back on your heels?..”
Therefore the verse confirms he will be killed and would not die a natural death.
The sunni hadith also confirms this.
Narrated Abdullah Ibn Massoud: “I am willing to take an oath nine times that the Prophet was murdered, but I am not willing to take an oath even once that he was not. This is because Allah made him a Prophet and a martyr as well.”
Source: Masnad Ahmed, Vol I, Page 408
It’s from this point onwards that Shia and sunni view on this subject diverge. While the sunni claim that the prophet was poisoned by the Jews, Shias stress that he was poisoned by his two wives Aisha and Hafsa, as commanded by their fathers Abu Bakr and Omar.
The belief that he died as a result of eating poison from the Jews is very unlikely for the following reason:
First, The incident of the poisoned meat took place in the year 7AH. (After the migration to media, also known as the Hijrah, which marks the 1st year of the Islamic lunar calendar), the prophet (pbuh&hf) died in the 11th year AH. This leaves a time gap of 4 years from when he allegedly ate the poisoned mean till his death. It is very unlikely that a person dies because of a poison he had taken so many years ago. It is also because generally the effect of poison is immediate and even if it takes time it cannot exceed a few months in which the health condition deteriorates gradually. In the case of the Prophet, we notice that he had been in the peak of his health and throughout the said four years he had no unusual health complaints. He would participate in the battles to defend Muslims as usual. Thus, it defies any logic that his health deteriorated suddenly and he died of a poison he had had taken more than four years ago despite the fact that he enjoyed good health throughout that intervening period.
Second, the story of his death by poison ingested 4 years before, was narrated by Aisha her self, we know that she has lied to her husband on several occasions and a woman, who would not abstain from lying to the noblest prophet, would not abstain from lying to ordinary people, either. Therefore, the Hadiths reported by her cannot be trusted, especially when she, herself, was accused of being involved in the murder of the Prophet.
Third, Aisha contradicted herself by claiming that he died of a tumor
Narrated Aisha: “Allah’s Prophet, (Peace be upon him), died of an internal tumor”!
Source: Masnad Abu Yoalla, Vol. 8, Page 258.
This confusion itself points fingers at her and even gives rise to suspicions about her.
Now, the shia view of the incident is as follows:
Narrated Ali ibn Ibrahim: “The Prophet said to Hafsa: I will tell you a secret. If you divulge it, Allah, His Angels and people will curse you. So, what is it? wondered Hafsa. The Prophet said: Abu Bakr will be able to seize the Caliphate and power after me, and will be succeeded by your father, Omar. Hafsa wondered: Who informed you of this?. (the prophet answered ) Allah, the Omnipresent, the Omniscient informed me. On the same day, Hafsa divulged the secret to her friend, Ayesha. In turn, Ayesha divulged the secret to her father, Abu Bakr. So, Abu Bakr came to Omar and said: My daughter Ayesha told me a secret reported by Hafsa, but I cannot always trust what Ayesha says. So, you ask your daughter Hafsa, make sure and tell me. Omar went over to Hafsa, and asked her. In the beginning, she was startled and denied it. But, Omar said to her: If you have indeed heard this secret, then, tell us so we can immediately seize power and get rid of Muhammad”. So, Hafsa said, yes, he told me that. At this point, those four got together and conspired to poison the Prophet”
Source: Tafseer al- Qommi, Vol 2, Page 367, Bihar-ul- Anwar by Allama al-Majlisi, Vol 22, Page 239
In another hadith, the prophet’s great grandson imam al-sadiq (as) accuses Aisha and Hafsa of poisoning his great grandfather.
Muhammad Ibn Massoud al-Ayashi related:
Imam al-Sadiq (Peace be upon him) was sitting with a group of his followers, and asked them: “Do you know whether the Prophet died a natural death or was murdered? Allah the Almighty says: “if then he died or is killed”. The truth is that the Prophet was poisoned in his last days before he died . Aisha and Hafsa administered poison in his food. Upon hearing this, Imam Sadiq’s followers said that they (Aisha, Hafsa) and their fathers were among the worst villains ever created by Allah.”
Source: Tafseer al-Ayashi, Vol 1, Page 200; Bihar-ul-Anwar, by Allama Al-Majlisi, Vol 22, Page 516