It should also be noted that Satan often takes the form of an angel of light. The abusive behavior of Mohammad's "Angel" and his lack of knowlage to the fact that Mohammad was illiterate, and the pure nonsense of the first "sura" (verse) atributed to the birth of Islam should make any sane person question the validity of Islam. Then there's the fact muhammad thought himself as possesed by a demon, and attempted suicide.
Then his "angel" never visited him again for a couple years.
It was during this time his first wife conspired with mohammad to create the illusion that he was a prophet. However,most in his tribe knew him as the retarded kid who had fits. It's also speculated that Mohammad killed his old wife, and that is when he became the Prophet of doom.
Plus there is the fact that after his "visitation" and self-declared prophet status, he murdered a fruit merchant and stole his donkey to travel on as he preached. None of the Old Testament Patriarchs and Prophets or Christian Apostles ever violated a Commandment in order to carry out their mission.