A controversial Muslim leader from Sydney, Australia says Muhammad was a Christian until age 40.
Mufti Mostafa Rashed also said on a TV broadcast that Muhammad was the assistant to a Christian preacher named Waraqa Bin Nofal, and that his first wife, Khadija, was also Christian.
Another Muslim scholar from Al-Azhar University who also participated in the program denied the claim.
Some Muslims on social media were enraged at Rasheed's assertion that Muhammad was once a Christian.
Zahim Alshamri, a Twitter user in Saudi Arabia, wrote, "Now this has crossed the limits of madness. He took some serious drugs. May Allah erase you and your mind."
In the sixth century when Islam began, it's believed the majority of the people of Arabia were still pagan. But Christianity had spread throughout the Middle East.
Rashed has generated controversy in the past by saying Muslims should be allowed to drink alcohol and that Muslim women are not required to wear the burqa.
The burqa comment caused a brawl to erupt among guests on a live TV program.