Reciting Tashahhud instead of Surah Al-Fatihah during Salah

A: If an Imam (the one who leads congregational Prayer) or a Munfarid (one praying alone) forgets to recite Surah Al-Fatihah and does not remember until after the Ruku‘, they are obligated to stand back again to recite Al-Fatihah and then recite some Ayahs (Qur’anic verses) from the Qur’an, if this occurs before reciting the first Tashahhud. If it occurs after reciting the first Tashahhud, they should just recite Al-Fatihah, perform the Ruku‘, and complete their Salah, ending with Sujud-ul-Sahw. This is because reciting Surah Al-Fatihah is a Rukn (integral pillar) of Salah, and it will not be valid without reciting it. In the case of a Ma’mum praying behind an Imam who forgets Al-Fatihah, they should continue with the Ruku‘; they should not stand back to recite Al-Fatihah after rising from the Ruku‘, because this is not obligatory on them as the position where it should be recited has passed.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.