Musnad Ahmad 27:1367

'Affan narrated to us, Wuhayb narrated to us, Musa ibn 'Uqbah narrated to us, Salim narrated to me, from 'Abdullah, regarding the dream of the Messenger of Allah (peace and blessings of Allah be upon him) about Abu Bakr and 'Umar. He said: "I saw the people gathered, then Abu Bakr stood up and drew a bucket or two, and in his drawing there was weakness, and may Allah forgive him. Then Ibn al-Khattab stood up, and it transformed into a large bucket, and I have not seen a genius among the people who could perform his feat, until the people watered their camels and rested them."