The Messenger of Allah ﷺ said, "Whoever performs a prayer in which he does not recite the Mother of the Quran, it is deficient, it is deficient, it is deficient, incomplete."I said, "Abu Hurayrah, sometimes I am behind the imam."He squeezed my arm and said, "Recite it silently to yourself, Persian, for I heard the Messenger of Allah ﷺ say that Allah the Exalted said, 'I have divided the prayer between Myself and My servant into two halves, half of it is for Me and half of it is for My servant, and My servant shall have what he asks for.'"The Messenger of Allah ﷺ said, "Recite. The servant says, 'All praise belongs to Allah, Lord of all the worlds' [Fatihah 1:2]. Allah says, 'My servant has praised Me.' The servant says, 'The Most Gracious, the Most Merciful' [Fatihah 1:3]. Allah
says, 'My servant has extolled Me.' The servant says, 'Master of the Day of Judgment' [Fatihah 1:4]. Allah
says, 'My servant has glorified Me.' The servant says, 'You alone we worship, and You alone we ask for help' [Fatihah 1:5]. Allah says, 'This is between Me and My servant, and My servant shall have what he asks for.' The servant says, 'Guide us to the straight path, the path of those You have blessed, not of those who have incurred Your wrath, nor of those who have gone astray' [Fatihah 1:6–7]. Allah says, 'These are for My servant, and My servant shall have what he asks for.'"
حدثنا القعنبي عن مالك عن العلاء بن عبد الرحمن أنه سمع أبا السائب مولى هشام بن زهرة يقول سمعت
قال رسول الله ﷺ من صلى صلاة لم يقرأ فيها بأم القرآن فهي خداج فهي خداج فهي خداج غير تمام قال فقلت يا أبا هريرة إني أكون أحيانا وراء الإمام قال فغمز ذراعي وقال اقرأ بها يا فارسي في نفسك فإني سمعت رسول الله ﷺ يقول قال الله تعالى قسمت الصلاة بيني وبين عبدي نصفين فنصفها لي ونصفها لعبدي ولعبدي ما سأل قال رسول الله ﷺ اقرءوا يقول العبد {الحمد لله رب العالمين} يقول الله عز وجل حمدني عبدي يقول {الرحمن الرحيم} يقول الله عز وجل أثنى علي عبدي يقول العبد {مالك يوم الدين} يقول الله عز وجل مجدني عبدي يقول العبد {إياك نعبد وإياك نستعين} يقول الله هذه بيني وبين عبدي ولعبدي ما سأل يقول العبد {اهدنا الصراط المستقيم صراط الذين أنعمت عليهم غير المغضوب عليهم ولا الضالين} يقول الله فهؤلاء لعبدي ولعبدي ما سأل
Muslim narrated it in "the Prayer," chapter "The obligation of reciting Fatihah in every rakat," etc., Hadith 395, from Malik's hadith by this route, and it is in the Muwatta (Yahya's version) 1/84, 85 (and Qanabi's version, p. 137-139).