“Ubadah b. al-samit came to late to lead the morning prayer. Abu Nu’aim, the mu’adhdhin, pronounced the takbir and he led the people in prayer. Then Ubadah came and I was with him. We Joined the row behind Abu Nu’aim, while Abu Nu’aim was reciting the Quran loudly. Then ‘Ubadah began to recite the Umm al-Quran (I.e Surah al Fatihah). When he finished, I said to Ubadah: I heard you reciting the Umm al-Quran while Abu Nu’aim was reciting Quran loudly. He replied: yes> The Messenger of Allah (ﷺ) led us in a certain prayer in which the Quran is recited loudly, but he became confused in the recitation. When he finished he turned his face to us and said: Do you recite when I recite the Quran loudly? Some of us said: we do so; this is why I said to myself: What is that which confused me (in the recitation of ) the Quran. Do not recite anything from the Quran when I recite it loudly except the Umm al-Quran.
Sunan Abi Dawud Book 2, Hadith 434