Sunan Abi Dawud Book 42, Hadith 42
Messenger of Allah (ﷺ)! I saw (in a dream) that a bucket was hung from the sky. Abu Bakr came, caught hold of both ends of its wooden handle, and drank a little of it. Next came ‘Umar who caught hold of both ends of its wooden handle and drank of it to his fill. Next came ‘Uthman who caught hold of both ends of its handle and drank of it to his fill. Next came ‘All. He caught hold of both ends of its handle, but it became upset and some (water) from it was sprinkled on him.
Last night a good man had a vision in which Abu Bakr seemed to be joined to the Messenger of Allah (ﷺ). ‘Umar to Abu Bakr, and ‘Uthman to ‘Umar. Jabir said: When we got up and left the Messenger of Allah (ﷺ), we said: The good man is the Messenger of Allah (ﷺ), and that their being joined together means that they are the rulers over this matter with which Allah has sent His Prophet (ﷺ).
Abu Dawud said: It has been transmitted by Yunus and Shu’aib, but they did not mention ‘Amr b. Aban.
The Romans will enter the Levant and stay there for forty days, and no place will be saved from them but Damascus and 'Uman.