Full Sharh — Bulugh al-Maram 408
وَعَنْ أَبِي سَعِيدٍ اَلْخُدْرِيِّ - رضى الله عنه - قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِذَا شَكَّ أَحَدُكُمْ فِي صَلَاتِهِ , فَلَمْ يَدْرِ كَمْ صَلَّى أَثْلَاثًا أَوْ أَرْبَعًا ? فَلْيَطْرَحِ الشَّكَّ وَلْيَبْنِ عَلَى مَا اسْتَيْقَنَ , ثُمَّ يَسْجُدُ سَجْدَتَيْنِ قَبْلَ أَنْ يُسَلِّمَ , فَإِنْ كَانَ صَلَّى خَمْساً شَفَعْنَ] لَهُ [ 1 صَلَاتَهُ , وَإِنْ كَانَ صَلَّى تَمَامً ا 2 كَانَتَا تَرْغِيمًا لِلشَّيْطَانِ" } رَوَاهُ مُسْلِمٌ . 31 - سقطت من الأصلين ، واستدركتها من الصحيح " وهي موجودة في المطبوع من " البلوغ " و " الشرح " .2 - في مسلم : " إتماما لأربع ".3 - صحيح . رواه مسلم ( 571 ) . وترغيما : أي : إلصاقا لأنفه بالتراب ، والمراد : رده خاسئا . وإهانته وإذلاله .
English Translation
Narrated Abu Sa'id al-Khudri (RA):: Allah's Messenger (ﷺ) said: "When anyone of you is in doubt about his Salat (prayer) and does not know how many he has prayed, three or four (Rak'at) he should cast aside his doubt and base his prayer on what he is sure of. Then, he should perform two prostrations before Taslim (salutation). If he has prayed five Rak'at, they will make his Salat (prayer) an even number for him and if he has prayed exactly four, they (i.e. two prostrations) will be humiliation for the devil." .
Source
Bulugh al-Maram(بلوغ المرام)
The Book of Prayer
Hadith Number
408