مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1014
Prayer
Forgetfulness - Section 1
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسلم: «إِن أحدكُم إِذا قَامَ يُصَلِّي جَاءَهُ الشَّيْطَان فَلبس عَلَيْهِ حَتَّى لايدري كَمْ صَلَّى؟ فَإِذَا وَجَدَ ذَلِكَ أَحَدُكُمْ فَلْيَسْجُدْ سجدين وَهُوَ جَالس»
Abu Huraira reported God's Messenger as saying, “When one of you stands up to pray the devil comes to him and confuses him so that he does not know how much he has prayed. If any of you has such an experience he should perform two prostrations during the period when he sits.”* * i.e. before pronouncing the taslim. (Bukhari and Muslim.)
Mishkat al-Masabih, 1014مُتَّفَقٌ عَلَيْهِ (الألباني)