There are at least 2 sources that claim this
2- According to a special narration, narrated in some books (among them Sahih Bokhari, v.4, p.1618/ Sahih Muslim, v.4, p.1733/ Al-Maghazi, v.5, p.2159/ etc.), Ayesha was quoted saying: “I forcibly put some medicine in prophet Muhammad’s mouth. Then he pointed out to me with his hand showing that I shouldn’t do this. We thought that this is because an ill person wouldn’t like any drug…”
Imam al-Sadiq (as) 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. Ayesha and Hafsa administered poison in his food. Upon hearing this, the Imam Sadiq's followers said that they and their fathers were among the worst villains ever created by Allah."
The second source is suspicious. Who is Imam Sadiq? Muslims don't believe anyone can talk to Allah. Is the haditz reliable?
Searching Google for Aisha Poison Muhammad shows many results too.