I heard from a Jewish historian that Muhammed walked into a shul on Yom
Kippur and got most of the Islamic customs from what he saw. On Yom
Kippur we have five services (Ma'ariv, Shachris, Musaf, Mincha, Ne'ila)
and that's why the Muslims have five services daily. Another few examples
just on the side: The Jews then were not wearing shoes because they
probably did not own any non-leather shoes so Muslims pray barefoot.
Also, Muhammed noticed them facing one direction so Muslims face one
direction; the Jews fasted - Muslims have Ramadan.