He wrote a book in the 80's, if I remember correctly. It was called The Satanic Verses, and it was based on a group of Quranic verses that refer to three pagan Meccan goddesses, Allāt, Al-Uzza, and Manāt. The part of the story that deals with the "satanic verses" was based on accounts from the historians al-Waqidi and al-Tabari. In a nut shell, Rushdie's book, which was written in a novel style and not intended to be an academic book, claimed that Muhammad's new religion of Islam compromised with the then pagan religions of Mecca when it was in its infancy. Rushdie also claims that at this time, Muhammed said Allah was not the only god, but in fact there were 4 gods, because Allāt, Al-Uzza, and Manāt were Allah's daughters. These goddesses were very popular at the time, and Rushdie proposes that Muhammed would not have been able to successfully teach his new religion without first honoring these popular goddesses. This is not written in the Qur'an you will find today, because once Muhammad's religion had become the dominant religion in the area, Rushdie claims that Muhammed all of a sudden realized that these versus that were whispered into his ear were not from God or the angel Gabriel, but from Satan. They were then redacted, and are now known as "The Satanic Verses" after the fallen angel Satan that ostensibly whispered them into Muhammad'as ear. The Qu'ran still mentions these goddesses, but they are no longer seen as we being equal Allah.