Musnad Ahmad 246
It was narrated that ‘Umar bin al-Khattab said:
The last thing to be revealed was the verse on riba, but the Messenger of Allah (ﷺ) passed away and did not discuss it with us. So give up riba and doubtful things.
حَدَّثَنَا يَحْيَى، عَنِ ابْنِ أَبِي عَرُوبَةَ، حَدَّثَنَا قَتَادَةُ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، قَالَ قَالَ عُمَرُ رَضِيَ اللَّهُ عَنْهُ إِنَّ آخِرَ مَا نَزَلَ مِنْ الْقُرْآنِ آيَةُ الرِّبَا وَإِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قُبِضَ وَلَمْ يُفَسِّرْهَا فَدَعُوا الرِّبَا وَالرِّيبَةَ‏.‏