The last of the Quran to be revealed was the verse on usury. The Messenger of Allah ﷺ passed away without explaining it, so abandon usury and anything that raises doubt.
إن آخر ما نزل من القرآن آية الربا، وإن رسول الله ﷺ قبض ولم يفسرها، فدعوا الربا والريبة.
Ibn Majah (2276) and Ahmad (246) both narrated it through the hadith of Ibn Abu Aruba, "Qatada narrated to us, from Saeed bin Musayab, who said, Umar said," then he mentioned it. Its chain of transmission is sahih. Ibn Abu Aruba, who is Saeed bin Abu Aruba, became confused in his memory later in life, but Yahya bin Saeed narrated it in Ahmad's version, and Khalid bin Harith narrated it in Ibn Majah's version, and both of them heard from him before his memory became confused.Sheikh Islam bin Taymiya and others used this hadith as evidence that the Prophet ﷺ explained the tafsir of the entire Quran, or most of it, to his companions. See Muqaddimah Usul Tafsir (p. 45). The tafsir of the Quran is meant to refer to its clarification, in line with the words of Allah Almighty, "And We sent down to you the message that you may make clear to the people what was sent down to them, and that they might reflect" [Nahl 16:44].