756 - It was narrated from ‘Ubadah ibn al-Samit that the Messenger of Allah (blessings and peace of Allah be upon him) said: “There is no prayer for the one who does not recite the Opening of the Book.”.

Commentary : Prayer has essential parts and obligatory parts without which it is neither valid nor complete. In this hadith, the Messenger of Allah (blessings and peace of Allah be upon him) confirms one of the essential parts of the prayer, which is reciting Surat al-Fatihah. He tells us that the prayer of one who does not recite the Opening of the Book (i.e., al-Fatihah) in every rak‘ah is not valid. Therefore reciting al-Fatihah is one of the essential parts of the prayer in every rak‘ah, and the prayer is not valid without it. The imam and the one who is praying on his own must recite it, and the one who is praying behind an imam should listen attentively when the imam recites it in prayers in which recitation is done out loud, because of the hadith narrated by Imam Muslim from Abu Musa al-Ash‘ari (may Allah be pleased with him), in which it says: “… then when he – meaning the imam – recites, listen attentively.”
This hadith indicates that it is enjoined to recite al-Fatihah in the prayer..