What Should A Person Who Stands Up Before Performing The Last Sitting In Prayer Do?

What should a person who stands up before performing the last sitting in prayer do?

If a person who is establishing prayer stands up before performing the last sitting by forgetfulness, he may complete his prayer by sitting back and performing sajdah al-sahw after reciting al-Tahiyyat unless he goes down into prostration.

If he did not perform prostration of the rakat from which he stood up, Imam Abu Hanifa and Imam Abu Yusuf say that it will not be possible for him to complete this prayer as a fardh prayer anymore. If the prayer that is being established consists of two or four rakats, he completes his prayer by establishing one more. By this way, he turns the prayer in to a nafl prayer. Afterwards, he needs to establish this fardh prayer again.

The reason for adding one more rakat to the prayer in the case above is because nafl prayers are established in even-numbered rakats. (Ibn Nujaym, al-Bahr, II, 112). If he is establishing maghrib prayer and did not perform the prostration of the rakat from which he stood up, he completes his prayer by sitting back and performing sajdah al-sahw as in above. If he did perform prostration of the rakat from which he stood up, then he is deemed to have established a four-rakat prayer. As the prayer that is established then turns into a nafl prayer, he needs to establish the fardh of maghrib prayer again.

Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWA