Abu Nadra reported:

We were in the company of Jabir b. 'Abdullah 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 dinars and mudds. We said: Who would be responsible for it? He said this prevention would be made by the Romans. He (Jabir b. Abdullah) kept quiet for a while and then reported Allah's Messenger ﷺ 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 'Umar b. 'Abd al-Aziz? They said: No (he would be Imam Mahdi).

حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَعَلِيُّ بْنُ حُجْرٍ، - وَاللَّفْظُ لِزُهَيْرٍ - قَالاَ حَدَّثَنَا إِسْمَاعِيلُ، بْنُ إِبْرَاهِيمَ عَنِ الْجُرَيْرِيِّ، عَنْ أَبِي نَضْرَةَ، قَالَ كُنَّا عِنْدَ جَابِرِ بْنِ عَبْدِ اللَّهِ فَقَالَ يُوشِكُ أَهْلُ الْعِرَاقِ أَنْ لاَ يُجْبَى إِلَيْهِمْ قَفِيزٌ وَلاَ دِرْهَمٌ . قُلْنَا مِنْ أَيْنَ ذَاكَ قَالَ مِنْ قِبَلِ الْعَجَمِ يَمْنَعُونَ ذَاكَ . ثُمَّ قَالَ يُوشِكَ أَهْلُ الشَّأْمِ أَنْ لاَ يُجْبَى إِلَيْهِمْ دِينَارٌ وَلاَ مُدْىٌ . قُلْنَا مِنْ أَيْنَ ذَاكَ قَالَ مِنْ قِبَلِ الرُّومِ . ثُمَّ سَكَتَ هُنَيَّةً ثُمَّ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " يَكُونُ فِي آخِرِ أُمَّتِي خَلِيفَةٌ يَحْثِي الْمَالَ حَثْيًا لاَ يَعُدُّهُ عَدَدًا " . قَالَ قُلْتُ لأَبِي نَضْرَةَ وَأَبِي الْعَلاَءِ أَتَرَيَانِ أَنَّهُ عُمَرُ بْنُ عَبْدِ الْعَزِيزِ فَقَالاَ لاَ .