Musnad Ahmad 30:888

Muhammad ibn Ja‘far narrated to us, he was asked about the recitation of the Imam in the prayers, he said: Shu‘bah narrated to us, from Abu Muhammad, from ‘Ata’ ibn Abi Rabah, from Abu Hurairah, who said: "In every prayer, there is recitation. So, whatever the Messenger of Allah (ﷺ) made us hear, we have made you hear, and whatever he kept hidden from us, we have kept hidden from you."