Abu Dawud Book 2, Hadith Number 822.
Chapter : Not known.
Narated By Ubadah ibn as-Samit : We were behind the Apostle of Allah (PBUH) at the dawn prayer, and he recited (the passage), but the recitation became difficult for him. Then when he finished, he said: Perhaps you recite behind your imam? We replied: Yes, it is so, Apostle of Allah. He said: Do not do so except when it is Fatihat al-Kitab, for he who does not recite it is not credited with having prayed.