Musannaf Ibn Abi Shaybah

Hazrat Abdur Rahman bin Auf narrates that when the Messenger of Allah (peace and blessings be upon him) conquered Makkah, he set out towards Taif and besieged the people of Taif for eighteen or nineteen (days), but could not conquer Taif. Then, one morning or one evening, he intensified the siege. Then the Messenger of Allah (peace and blessings be upon him) camped, and at midday he set out and said: O people! I will reach (the destination) before you, so I advise you to goodness with my honor. And know for sure that the place of my promise with you is the Hawd (the Pond). By the One in Whose hand is my soul, you must establish prayer and you must pay zakat, or I will send to you one man from among myself, like myself, who will strike the necks of those who fight (the believers) and will take their people captive. The narrator says: People thought that this man would be Hazrat Abu Bakr or Hazrat Umar. But the Noble Prophet (peace and blessings be upon him) took the hand of Hazrat Ali (may Allah be pleased with him) and said: This is the man.