Musnad Ahmad 30:3515

Rawh narrated to us, Muhammad ibn Abi Hafsah narrated to us, Ibn Shihab narrated to us, from Abu Salamah ibn Abd al-Rahman and Abu Abdullah al-Agharr, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "At every door of the mosque on the day of Friday, there are angels writing down the arrival of the people. When the Imam sits, the scrolls are folded. The one who arrives early is like one who offers a camel as a sacrifice, the one who follows him is like one who offers a cow, the one who follows him is like one who offers a sheep, the one who follows him is like one who offers a chicken, and the one who follows him is like one who offers an egg."