Sahih Bukhari Volume 1, Book 10, Hadith 608

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ إِذَا نُودِيَ لِلصَّلاَةِ أَدْبَرَ الشَّيْطَانُ وَلَهُ ضُرَاطٌ حَتَّى لاَ يَسْمَعَ التَّأْذِينَ، فَإِذَا قَضَى النِّدَاءَ أَقْبَلَ، حَتَّى إِذَا ثُوِّبَ بِالصَّلاَةِ أَدْبَرَ، حَتَّى إِذَا قَضَى التَّثْوِيبَ أَقْبَلَ حَتَّى يَخْطُرَ بَيْنَ الْمَرْءِ وَنَفْسِهِ، يَقُولُ اذْكُرْ كَذَا، اذْكُرْ كَذَا‏.‏ لِمَا لَمْ يَكُنْ يَذْكُرُ، حَتَّى يَظَلَّ الرَّجُلُ لاَ يَدْرِي كَمْ صَلَّى ‏"‏‏

Narrated By Abu Huraira : Allah's Apostle said, "When the Adhan is pronounced Satan takes to his heels and passes wind with noise during his flight in order not to hear the Adhan. When the Adhan is completed he comes back and again takes to his heels when the Iqama is pronounced and after its completion he returns again till he whispers into the heart of the person (to divert his attention from his prayer) and makes him remember things which he does not recall to his mind before the prayer and that causes him to forget how much he has prayed."