Musnad Ahmad 962:131

Abu al-Nadr narrated to us, Mubarak—meaning Ibn Fudalah—narrated to us, Abu Ghalib narrated to me, from Abu Umamah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The angels sit on the doors of the mosque on the day of Friday, with them are the scrolls, writing down the people. So when the Imam comes out, the scrolls are folded." I said: "O Abu Umamah, is there no Friday [prayer reward] for the one who comes after the Imam has come out?" He said: "Yes, but he is not among those who are written in the scrolls."