: After reciting tashahhud in the first sitting of four rak'at or three rak'at prayers, if one forgets the amount of three tasbeehs and stands late, or if durud and doa mashura fall, then sahu must be prostrated. (Almuhitul Burhani 2/313 ; Sharhul Muniyah 460) In the third and fourth rak'ahs of the obligatory prayer , no other surah is added after Surah Fatihah , but if one accidentally adds another surah or recites Bismillah for the purpose of adding another surah, then Sahu prostration is not obligatory. (Alamgiri 1/126 , Aap K Masael 4/59)