If one forgets a prostration from the first unit and remembers it in the second
Machine translationRead the Arabic original
The questioner:
Honorable Shaykh, may Allah grant you success. He says: If I forget a pillar of the prayer, for example prostration, and I prostrate only once, then I stand up for the second unit, and I remember during the prayer that I did not perform but one prostration. He says: What is obligatory for me in that case?
The Shaykh:
If you have entered the second unit and you do not remember after you have entered the second unit, then the first unit is void, and the second unit becomes the first. But if you have not entered the second unit, you go back and perform the second prostration. Yes.
The questioner:
Honorable Shaykh, may Allah grant you success.
The Shaykh:
If you have said the closing salam or completed the prayer and you did not realize it until after you had said the salam, you perform a complete unit. Yes.
Honorable Shaykh, may Allah grant you success. He says: If I forget a pillar of the prayer, for example prostration, and I prostrate only once, then I stand up for the second unit, and I remember during the prayer that I did not perform but one prostration. He says: What is obligatory for me in that case?
The Shaykh:
If you have entered the second unit and you do not remember after you have entered the second unit, then the first unit is void, and the second unit becomes the first. But if you have not entered the second unit, you go back and perform the second prostration. Yes.
The questioner:
Honorable Shaykh, may Allah grant you success.
The Shaykh:
If you have said the closing salam or completed the prayer and you did not realize it until after you had said the salam, you perform a complete unit. Yes.
Source
المنتقى من أخبار سيد المرسلين 03-01-1434هـ — alfawzan.live (57:26)
The Arabic text is a machine transcription of the audio recording.