Sahih Muslim Book 41, Hadith Number 6961.
Abu Nadra reported: “We were in the company of Jabir b. ‘Abdulldh that he said it may happen that the people of Iraq may not send their qafiz and dirhams (their measures of food stuff and their money). We said: Who would be responsible for it? He said: The non-Arabs would prevent them. He again said: There is the possibility that the people of Syria may not send their dinar and mudd. We said: Who would be responsible for it? He said This prevention would be made by the Romans. He (Jabir b. Abdullab) kept quiet for a while and then reported Allah’s Messenger (may peas be upon him) having said There would be a caliph in the last(period) of my Ummah who would freely give handfuls of wealth to the people without counting it. I said to Abu Nadra and Abu al-‘Ala: DO you mean ‘Umarb. ‘Abd al-Aziz? They said: No (he would be Imam Mahdi.).