Sahih Bukhari Volume 5, Book 57, Hadith Number 16.
Narated By Abu Huraira : I heard Allah’s Apostle saying, “While I was sleeping, I saw myself standing at a well, on it there was a bucket. I drew water from the well as much as Allah wished. Then Ibn Abi Quhafa (i.e. Abu Bakr) took the bucket from me and brought out one or two buckets (of water) and there was weakness in his drawing the water. May Allah forgive his weakness for him. Then the bucket turned into a very big one and Ibn Al-Khattab took it over and I had never seen such a mighty person amongst the people as him in performing such hard work, till the people drank to their satisfaction and watered their camels that knelt down there.”