Abu al-Sa'ib, the freed slave of Hisham bin Zuhrah, narrates that he heard Sayyiduna Abu Hurayrah (may Allah be pleased with him) saying that the Messenger of Allah (peace and blessings be upon him) said: "Whoever does not recite Surah al-Fatihah in the prayer, that prayer is deficient and incomplete," and he said this three times. Abu al-Sa'ib said: I asked: O Abu Hurayrah, sometimes I am praying behind an imam? Sayyiduna Abu Hurayrah (may Allah be pleased with him) took hold of my arm and said: O Persian, recite it within yourself, for I heard the Messenger of Allah (peace and blessings be upon him) saying that Allah Almighty says: "I have divided the prayer between Myself and My servant; half of it is for Me and half of it is for My servant, and My servant shall have what he asks."
The Messenger of Allah (peace and blessings be upon him) said: "Recite it. When the servant says: 'All praise is for Allah, the Lord who sustains all the worlds,' Allah Almighty says: My servant has praised Me. When the servant says: 'The Most Gracious, the Most Merciful,' Allah Almighty says: My servant has extolled Me. When the servant says: 'Master of the Day of Recompense,' Allah Almighty says: My servant has glorified Me. When the servant says: 'You alone we worship and from You alone we seek help,' Allah Almighty says: This verse is between Me and My servant, and My servant shall have what he asked. And the servant says: 'Guide us to the straight path, the path of those upon whom You have bestowed favour, not of those upon whom anger has fallen, nor of those who are astray,' and Allah Almighty says: This is for My servant, and My servant shall have what he asked."
(b) The wording of the above hadith is that of Qutaybah, and in the hadith of al-Qa'nabi it is that when the servant says: 'Master of the Day of Judgement,' Allah Almighty says: "My servant has glorified and exalted Me, and this is between Me and My servant." The rest of the hadith is the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2366