Sahih Muslim Hadith 4086

I asked Ibn Abbas ( رضی اللہ عنہ) about the conversion (of gold and silver for silver and gold). We said: Is it hand to hand exchange? I said: Yes. whereupon he said: There is no harm in it. I informed Abu Sa'id رضی اللہ عنہ about it, telling him that I had asked Ibn 'Abbas رضی اللہ عنہ about it and he said: Is it hand to hand exchange? I said: Yes, whereupon he said: There is no harm in it. He (the narrator) said, or he said like it: We will soon write to him, and he will not give you this fatwa (religious verdict). He said: By Allah, someone of the boy-servants of Allah's Messenger ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌) brought dates, but he refused to accept them (on the plea) that those did not seem to be of the dates of our land. He said: Something had happened to the dates of our land, or our dates. So I got these dates (in exchange by giving) excess (of the dates of our land), whereupon he said: You made an addition for getting the fine dates (in exchange) which tantamounts, to interest; don't do that (in future). Whenever you find some doubt (as regards the deteriorating quality of) your dates, sell them, and then buy the dates that you like.