Mishkat al-Masabih 11 Business Transactions كتاب البيوع 69

وَعَنْ عُمَرَ بْنِ الْخَطَّابِ رَضِيَ اللَّهُ عَنْهُ إِنَّ آخِرَ مَا نَزَلَتْ آيَةُ الرِّبَا وَإِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قُبِضَ وَلَمْ يُفَسِّرْهَا لَنَا فَدَعُوا الرِّبَا وَالرِّيبَةَ. رَوَاهُ ابْن مَاجَه والدارمي

‘Umar b. al-Khattab said: The last verse to be sent down was that on usury (Al-Qur’an 2:275) but God’s Messenger was taken without having expounded it to us; so leave aside usury and whatever is doubtful. Ibn Majah and Darimi transmitted it.