Sahih Muslim Book - 4, Hadith - 859

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ حَدَّثَنَا الْمُغِيرَةُ يَعْنِي الْحِزَامِيَّ عَنْ أَبِي الزِّنَادِ عَنِ الْأَعْرَجِ عَنْ أَبِي هُرَيْرَةَ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ إِذَا نُودِيَ لِلصَّلَاةِ أَدْبَرَ الشَّيْطَانُ لَهُ ضُرَاطٌ حَتَّى لَا يَسْمَعَ التَّأْذِينَ فَإِذَا قُضِيَ التَّأْذِينُ أَقْبَلَ حَتَّى إِذَا ثُوِّبَ بِالصَّلَاةِ أَدْبَرَ حَتَّى إِذَا قُضِيَ التَّثْوِيبُ أَقْبَلَ حَتَّى يَخْطُرَ بَيْنَ الْمَرْءِ وَنَفْسِهِ يَقُولُ لَهُ اذْكُرْ كَذَا وَاذْكُرْ كَذَا لِمَا لَمْ يَكُنْ يَذْكُرُ مِنْ قَبْلُ حَتَّى يَظَلَّ الرَّجُلُ مَا يَدْرِي كَمْ صَلَّى.

It was narrated from Abu Hurairah that the Prophet (s.a.w) said: "When the call to prayer is given, the Shaitan runs away, breaking wind so that he cannot hear the call. When the call is over, he comes back, until the Iqamah for prayer is given, then he runs away. Then when the Iqamah is over he comes back and tries to distract a man, saying to him, 'Remember such and such, remember such and such,' reminding him of things that he did not remember before, until he does not know how many (Rak'ah) he has prayed."