Sahih Bukhari Volume 005, Book 057, Hadith Number 025.

Narated By Abdullah bin Umar : Allah's Apostle said. "While (in a dream), I was standing by a well, drawing water from it. Abu Bakr and 'Umar came to me. Abu Bakr took the bucket (from me) and drew one or two buckets of water, and there was some weakness in his drawing. May Allah forgive him. Then Ibn Al-Khattab took the bucket from Abu Bakr, and the bucket turned into a very large one in his hands. I had never seen such a mighty person amongst the people as him in performing such hard work. He drew so much water that the people drank to their satisfaction and watered their camels." (Wahab, a sub-narrator said, "till their camels drank and knelt down.")