I am already familiar with Quranic references against riba (such as Quran 2:275-280) and a number of ahadith, but the issue for me is the meaning which the prophet attached to riba. In his hadith, Caliph Umar, a companion of the prophet, was not clear on what the prophet meant by riba.
Prof. Farooq in this article in the Arab Law Quarterly, makes a good case that riba as understood at the time of the prophet (riba al jahiliya) was the excessive increase levied by moneylenders ("redoubling") in outstanding debt of poor debtors who did not pay repay debt when due, and that the original interest or markup - "stipulated increase" - was not riba. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1412753 . Mufti Taqi Usmani disagrees with this idea.
I am not interested here in the debatable economic rationales which scholars may advance for prohibiting interest, and which in any case are not discussed by the prophet.