The Prophet ﷺ said, "Whoever performs a prayer in which he does not recite the Mother of the Quran, it is deficient," repeating this three times, "incomplete."It was said to Abu Hurairah, "We are sometimes behind the imam."He replied, "Recite it to yourself, for I heard the Messenger of Allah ﷺ say, 'Allah the Exalted has said, I have divided the prayer between Myself and My servant into two halves, and My servant shall have what he asks for. When the servant says, "All praise belongs to Allah, Lord of the worlds" [Fatihah 1:2], Allah the Exalted says, My servant has praised Me. When he says, "The Most Merciful, the Especially Merciful" [Fatihah 1:3], Allah the Exalted says, My servant has extolled Me. When he says, "Master of the Day of Judgment" [Fatihah 1:4], He says, My servant has glorified Me." On another occasion he said, "My servant has entrusted himself to Me. When he says, "You alone we worship, and You alone we ask for help" [Fatihah 1:5], He says, This is between Me and My servant, and My servant shall have what he asks for. When he says, "Guide us to the straight path, the path of those upon whom You have bestowed favor, not of those who have earned Your anger nor of those who go astray" [Fatihah 1:6–7], He says, This is for My servant, and My servant shall have what he asks for.'"Sufyan said, "Ala bin Abdul-Rahman bin Yaqub narrated this to me. I went in to see him while he was ill in his house, and I asked him about it myself."
و حدثناه إسحق بن إبراهيم الحنظلي أخبرنا سفيان بن عيينة عن العلاء عن أبيه
عن النبي ﷺ قال من صلى صلاة لم يقرأ فيها بأم القرآن فهي خداج ثلاثا غير تمام فقيل لأبي هريرة إنا نكون وراء الإمام فقال اقرأ بها في نفسك فإني سمعت رسول الله ﷺ يقول قال الله تعالى قسمت الصلاة بيني وبين عبدي نصفين ولعبدي ما سأل فإذا قال العبد {الحمد لله رب العالمين} قال الله تعالى حمدني عبدي وإذا قال {الرحمن الرحيم} قال الله تعالى أثنى علي عبدي وإذا قال {مالك يوم الدين} قال مجدني عبدي وقال مرة فوض إلي عبدي فإذا قال {إياك نعبد وإياك نستعين} قال هذا بيني وبين عبدي ولعبدي ما سأل فإذا قال {اهدنا الصراط المستقيم صراط الذين أنعمت عليهم غير المغضوب عليهم ولا الضالين} قال هذا لعبدي ولعبدي ما سأل قال سفيان حدثني به العلاء بن عبد الرحمن بن يعقوب دخلت عليه وهو مريض في بيته فسألته أنا عنه