It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) 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." Abu al-Sa'ib says: I said to Sayyiduna Abu Hurayrah (may Allah be pleased with him): Sometimes I am behind the imam. So he 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 into two halves. Half of it is for Me and half of it is for My servant, and My servant shall have what he has asked for. When the servant says: 'All praise is for Allah, the Lord of all the worlds' [Surah al-Fatihah: 2], Allah Almighty says: 'My servant has praised Me.' When the servant says: 'The Most Gracious, the Most Merciful' [Surah al-Fatihah: 3], Allah Almighty says: 'My servant has extolled Me.' And when the servant says: 'Master of the Day of Recompense' [Surah al-Fatihah: 4], Allah Almighty says: 'My servant has glorified Me.' When the servant says: 'You alone we worship and You alone we ask for help' [Surah al-Fatihah: 5], Allah Almighty says: 'This is between Me and My servant, and My servant shall have what he has asked for.'"
In the hadith of al-Walid bin Kathir it is: When the servant says: 'Master of the Day of Resurrection' [Surah al-Fatihah: 4], Allah Almighty says: "My servant has glorified Me. This is for Me, and the rest is for My servant." When the servant says: 'You alone we worship and You alone we ask for help' [Surah al-Fatihah: 5]; then he recited the whole surah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2927