Musnad Abu Ya'la al-Mawsili 42:398

Zuhayr narrated to us, Isma'il narrated to us, from al-Jurayri, from Abu Nadrah, who said: I asked Ibn 'Abbas about *al-sarf* (currency exchange). He said: "Hand to hand." I said: "Yes." He said: "There is no harm in it." He said: So I met Abu Sa'id and informed him that I had asked Ibn 'Abbas about *al-sarf* and he said: "There is no harm in it." He said—or he said that—: "As for us, we shall write to him so that he does not issue you a fatwa regarding it." He said: By Allah, some of the young men of the Messenger of Allah (ﷺ) came with dates, and he disapproved of them. He said: "It is as if these are not from the dates of our land." He said: "There was something in the dates of the year, so I took these and added some increase." He said: "You have doubled, you have practiced usury (*riba*). Do not approach this. If you are in doubt about anything of your dates, then sell them, then buy the dates you desire."