Musnad Ahmad 30:2633

Waki’ narrated to us, from Harun al-Thaqafi, who said: I heard ‘Ata’ [saying], from Abu Hurayrah, who said: "In every prayer there is recitation. So, whatever the Messenger of Allah (peace and blessings of Allah be upon him) made us hear, we have made you hear; and whatever he did not make us hear, we have not made you hear."