The Prophet (peace and blessings of Allaah be upon him) was affected by the poisoned mutton that he ate in Khaybar
Question

                Some people doubt that the prophet may have died from poisoning. As a result of eating from the poisoned sheep that was offered to him by the Jewish woman, is this true?.
Praise be to Allah.It is proven by the scholars who studied the Prophet’s biography in detail that he ate mutton that had been poisoned by a Jewish woman in Khaybar, then the leg of mutton spoke and informed the Prophet  (peace and blessings of Allaah be upon him) that it was poisoned, so he stopped eating it. When his final illness came, he  (peace and blessings of Allaah be upon him) said: “O ‘Aa’ishah, I still feel the pain of the food that I ate in Khaybar, and this time I feel that my aorta is being cut from that poison.” Narrated by al-Bukhaari in his Saheeh. So there is no room for doubt that this poison affected his body, since it is proven in  al-Saheeh and elsewhere. 
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote. 
Standing Committee for Academic Research and Issuing Fatwas 
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-‘Azeez Aal al-Shaykh, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh Saalih al-Fawzaan, Shaykh Bakr Abu Zayd