Is it obligatory for the congregant to repeat the rak'ah if he forgot to recite Al-Fatihah in a loud prayer, or does the Imam bear that responsibility on his behalf? And what is the majority's response to the two hadiths that contradict their fatwa that it is not obligatory for the congregant to recite Al-Fatihah in a loud prayer?

The Shafi'is hold that the follower (ma'mum) must recite Al-Fatiha in every rak'ah. If one forgets it in a rak'ah, they must repeat that rak'ah. Imam An-Nawawi is of the view that if the follower bows with the imam and then remembers having forgotten Al-Fatiha, they are not permitted to go back and recite it. Instead, they must perform an additional rak'ah after the imam concludes the prayer with the salutation.

The hadith (definition) of Abu Bakra is not related to this issue, because the Shafi'is waive the requirement of reciting Al-Fatiha for someone who joins the imam while he is bowing, as the place for its recitation (standing) has been missed. This differs from the view of Al-Bukhari and the Zahiris, who do not consider the rak'ah valid for someone who only catches the bowing.

As for the hadith: "Do not do anything except with the Mother of the Book (Umm al-Kitab)," the majority of scholars have deemed it weak because it is narrated by Muhammad ibn Ishaq, or they have said that it is contradicted by the verse: "And when the Qur'an is recited, then listen to it and pay attention," and the hadith: "And when he (the Imam) recites, then listen attentively."

This issue is among the major matters of fiqh, and the disagreement concerning it is permissible. There is no blame on anyone who chooses one opinion or follows a trustworthy scholar in this regard.