Iyad (may Allah have mercy on him) says that I asked Hazrat Abu Sa'id Khudri (may Allah be pleased with him) that sometimes one of us is praying and he does not remember how many rak'ahs he has prayed? He replied that the Prophet (peace and blessings of Allah be upon him) said: When any one of you is praying and does not remember how many rak'ahs he has prayed, he should perform two prostrations of forgetfulness while sitting. And when Satan comes to any one of you and says that your ablution has broken, then tell him that you are lying, unless he smells something in his nose or hears its sound in his ears.