Mishkat al-Masabih 854
‘Ubada b. as-Samit said:
We were behind the Prophet at the dawn prayer, and he recited a passage, but the recitation became difficult for him. Then when he finished he said, “Perhaps you recite behind your imam?” We replied, “Yes, Messenger of God.” He said, “Do it only when it is Fatihat al-Kitab , for he who does not include it in his recitation is not credited with having prayed.” 

Abu Dawud and Tirmidhi transmitted it, and Nasa’i has something to the same effect. In a version by Abu Dawud he said, “I am wondering what is the matter with me that the Qur’an should be at variance with me. So do not recite any of the Qur’an when I recite aloud, except Umm al-Qur'an ."
وَعَنْ عُبَادَةَ بْنِ الصَّامِتِ قَالَ: كُنَّا خَلْفَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي صَلَاةِ الْفَجْرِ فَقَرَأَ فَثَقُلَتْ عَلَيْهِ الْقِرَاءَةُ فَلَمَّا فَرَغَ قَالَ: «لَعَلَّكُمْ تقرؤون خَلْفَ إِمَامِكُمْ؟» قُلْنَا: نَعَمْ يَا رَسُولَ اللَّهِ. قَالَ: «لَا تَفْعَلُوا إِلَّا بِفَاتِحَةِ الْكِتَابِ فَإِنَّهُ لَا صَلَاةَ لِمَنْ لَمْ يَقْرَأْ بِهَا» . رَوَاهُ أَبُو دَاوُدَ وَالتِّرْمِذِيُّ وَلِلنِّسَائِيِّ مَعْنَاهُ وَفِي رِوَايَةٍ لأبي دَاوُد قَالَ: «وَأَنا أَقُول مَالِي يُنَازعنِي الْقُرْآن؟ فَلَا تقرؤوا بِشَيْءٍ مِنَ الْقُرْآنِ إِذَا جَهَرْتُ إِلَّا بِأُمِّ الْقُرْآن»