Christians claimed that according to hadith, the Prophet Muhammad was poisoned by a Jewess from Khaybar who gave him poisoned mutton. He had himself cupped to heal from the poison.
The Quran never confirmed such incident had occurred on the Prophet.
However, clear evidence shows that the one who died of poison is not Muhammad accoding the scripture from God, the one who died of poison was the biblical Jesus.
Mark 15:35-37 And some of them that stood by, when they heard it, said, Behold, he calleth Elias. And one ran and filled a spunge full of vinegar, and put it on a reed, and gave him to drink, saying, Let alone; let us see whether Elias will come to take him down. And Jesus cried with a loud voice, and gave up the Ghost.
John 19:30 When Jesus therefore had received the vinegar, he said, It is finished: and he bowed his head, and gave up the Ghost,
Muhammad was never poisoned according to the Quran –
S3:111 They will not harm you except for some annoyance. And if they fight you, they will show you their backs; then they will not be aided.
Allah never failed to help His Prophet –
S22:15 If any think that Allah will not help him (His Messenger) in this world and the Hereafter, let him stretch out a rope to the ceiling and cut himself off: then let him see whether his plan will remove that which enrages him!
Muhammad died a normal death –
S21:34-35 And We did not grant to any man before you eternity [on earth]; so if you die would they be eternal? Every soul will taste death. And We test you with evil and with good as trial; and to Us you will be returned.
S29:57 Every soul will taste death. Then to Us will you be returned.
Pondering with Saifuddin's index 