What did Prophet Muhammad (saw) say about Satan coming and making us forget how many rak`at we have prayed?
 Narrated Abu Huraira:                     Allah's Apostle said, "When anyone of you stands for the prayers, Satan comes and puts him in doubts till he forgets how many rak`at he has prayed. So if this happens to anyone of you, he should perform two prostrations of Sahu while sitting.