Question
Whilst I was saying my Isha salah (4 fardh), I had to do sajdah sahw because of a mistake I made. The mistake was after 3 rakats, I sat down when I was supposed to go back up in qiyam position. I forgot to do sajdah sahw. Do, I have to repeat the salah?
Answer
If a Musalli omits a Waajib of Salaah, or delays it, advances it, adds it, omits it, or repeats it unintentionally, etc. in Salaah due to error then it is compulsory upon him to make Sajda-e-Sahw. If one did not perform Sajda-e-Sahw (due to forgetfulness) then it is Waajib upon him to repeat the Salaah as long as the Salaah time remains. If the Salaah time had expired but the Salaah was not repeated, then one will be sinful. However, the Fardh will be discharged, but in a deficient manner.
It will not be Waajib to repeat the Salaah once the Salaah time expires but it will be Mustahab (preferable) for one to do so (i.e. repeat the Salaah after the time).
Checked and Approved By:
Mufti Muhammed Saeed Motara Saheb D.B.
References
يجب سجدتان بتشهد وتسليم لترك واجب بتقديم او تاخير او زيادة او نقصان او تکرار سهوا
(مراقي ص ٢٥٠)
فالحاصل ان من ترك واجبا من واجباتها او ارتكب مكروها تحريما لزمه وجوبا ان يعيد في الوقت – فان خرج اثم ولا يجب جبر النقصان بعده – فلو فعل فهو افضل
(رد المحتار ص ٦٤ ج ٢ )