Ruling on the Salah of a person who doubted whether they recited Surah Al-Fatihah or not*
Q: Sometimes during my Salah (prayer) I become unsure whether I have recited Surah Al-Fatihah (the Opening Chapter of the Holy Qur'an) or not; should I offer two prostrations of forgetfulness? What should I recite in these two prostrations of forgetfulness? If it is probable that I have recited it, should I offer the two prostrations of forgetfulness?
A: If a person performing Salah alone or as an Imam is unsure whether he has recited Surah Al-Fatihah or not, he has to recite it again before bowing and offer two prostrations of forgetfulness before concluding the Salah. If they are in doubt after finishing the Salah, their Salah is valid and they should pay no attention to such doubt, as the Salah is basically correct unless there is hard evidence that it is incorrect. As for those praying behind the Imam, their Salah is correct even if they forgot to recite Surah Al-Fatihah as the recitation of the Imam will be sufficient for them like one who does not recite Surah Al-Fatihah out of ignorance and the one who joins the congregational Salah while the Imam is bowing. In case someone joins the Salah while the Imam is bowing, they should say "Takbir" (saying: "Allahu Akbar [Allah is the Greatest]") while they are upright and then bow. One is exempted from reciting Surah Al-Fatihah if one has not completed it with the Imam while he was standing for recitation, as mentioned in the Prophetic Hadith narrated by Abu Bakrah in this regard. As for the prostration of forgetfulness, a Muslim may recite the same supplications recited in the ordinary prostration of Salah. One can say, "Subhana Rabi Al-A`la (Glory be to my Lord, the Most High)" and other words of praise. May Allah grant us success.
(Part No. 11; Page No. 254)
* This was published in the book entitled, "Al Da'wah", vol. 1, pp. 79-80