Amr bin Shu'aib, on the authority of his father, narrates from his grandfather: The Prophet Muhammad (peace be upon him) said: "Whoever is performing an obligatory or voluntary prayer should recite Surah Al-Fatihah in it and along with it recite another Surah; if he only recites Surah Al-Fatihah, that will also suffice for him. And whoever is praying behind an Imam in a prayer in which the Imam recites aloud, he should recite Surah Al-Fatihah during the Imam's silence; if he does not do so, his prayer will be incomplete and not fulfilled." The narrator named Muhammad bin Abdullah bin Ubaid bin Umair is weak.