Musnad Ahmad 27:1020

Abu Dawud Umar ibn Sa'd narrated to us, Badr ibn Uthman narrated to us, from Ubayd Allah ibn Marwan, from Abu 'Aisha, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) came out to us one morning after sunrise and said: "I saw just before dawn as if I had been given the keys and the scales. As for the keys, they are these keys, and as for the scales, they are these with which you weigh. I was placed in a pan, and my nation was placed in a pan, and I was weighed against them and I outweighed them. Then Abu Bakr was brought and he was weighed against them and he outweighed them. Then Umar was brought and he was weighed and he outweighed them. Then Uthman was brought and he was weighed against them, then it was raised."