I heard Ibn Abbas issuing legal verdicts permitting currency exchange at unequal rates. So I gave verdicts based on that for some time. Then I met him later, and he had retracted that opinion.I asked him, "Why?"He replied, "It was merely an opinion I had formed. Abu Saeed Khudri narrated to me that the Messenger of Allah ﷺ forbade it."
سمعت ابن عباس يفتي بالصرف. قال: فأفتيت به زمانا قال: ثم لقيته، فرجع عنه. قال: فقلت له: ولم؟ فقال: إنما هو رأي رأيته. حدثني أبو سعيد الخدري أن رسول الله ﷺ نهي عنه.
Imam Ahmad narrated it (11447) from Waki, who said, "Sulayman bin Ali Rubai told us, he said, 'I heard Abu Jawza,'" then he related it. He also narrated it (11479) from Yazid bin Harun, who said, "Sulayman bin Ali Rubai informed us with his chain," and in it it states,"I asked Ibn Abbas about currency exchange hand to hand, and he said, 'There is no harm in that, two for one, more than that or less.'" He said, "Then I performed hajj another time, while the shaykh was still alive, so I went to him and asked him about currency exchange, and he said, 'Weight for weight.'" He said, "I said, 'You gave me a ruling of two for one, and I have kept giving that ruling ever since you told me.'" He said, "That was based on my own opinion, but here is Abu Saeed Khudri narrating from the Messenger of Allah ﷺ, so I have abandoned my opinion for the hadith of the Messenger of Allah ﷺ."Its isnad is sahih. Ibn Majah narrated it (2258) by another route from Hammad bin Zayd, from Sulayman bin Ali Rubai with his chain, in similar wording.Bayhaqi narrated it (2825) by another route from Maruf bin Saad, that he heard Abu Jawza say, "I served Ibn Abbas for nine years. Once a man came to him and asked him about one dirham for two dirhams. Ibn Abbas cried out and said, 'This man wants me to make him consume riba.' Some people around him said, 'We have been doing this on the strength of your ruling.'" Ibn Abbas said, "I used to give that ruling, until Abu Saeed and Ibn Umar told me that the Prophet ﷺ forbade it, so now I forbid it to you."It is established that Ibn Abbas and Ibn Umar retracted their position on currency exchange, which was the permissibility of an increase between things of the same kind if it was hand to hand, once the hadith of Abu Saeed Khudri reached them, as mentioned above, and as it comes in Sahih Muslim from the hadith of Abu Nadra, who said, "I later came to Ibn Umar, and he forbade me from it. But I did not go to Ibn Abbas." He said, "Abu Sahba told me that he asked Ibn Abbas about it in Makkah, and he disliked it."Likewise, Hakim narrated (2/42-43) by the route of Hayan Adawi, who said, "I asked Abu Mijlaz about currency exchange, and he said, 'Ibn Abbas saw no harm in it for a period of his life, so long as it was in kind for kind,' meaning hand to hand, 'and he used to say, riba is only in deferred payment. Then Abu Saeed Khudri met him and said to him, "Ibn Abbas, will you not fear Allah! How long will you keep feeding people riba? Has it not reached you that the Messenger of Allah ﷺ said one day, while he was with his wife Umm Salama, 'I really crave ajwa dates.'So she sent two saa of dates to a man from the Ansar, and he brought back one saa of ajwa dates in exchange for the two saa. She got up and presented it to the Messenger of Allah ﷺ. When he saw it, he liked it, and he took a date, then stopped and said, 'Where did you get this from?' Umm Salama said, 'I sent two saa of dates to a man from the Ansar, and he brought us this one saa in exchange for the two saa, and here it is in full.'"So he set the date down in front of him and said, "Return it, I have no need for it. Dates for dates, wheat for wheat, barley for barley, gold for gold, silver for silver, hand to hand, like for like, equal for equal, and whoever gives more, it is riba." Then he said, "The same applies to whatever is measured or weighed too."Ibn Abbas said, "May Allah reward you with paradise, Abu Saeed. You have reminded me of something I had forgotten. I ask Allah's forgiveness and I repent to Him."'" After that he forbade it in the strictest terms.Hakim said, "This is a hadith with a sahih isnad, and the two of them did not record it with this wording."Dhahabi said in Talkhis Mustadrak, "Hayan has some weakness in him, and he is not to be relied upon as proof." End of quote.Hayan is Ibn Ubaydullah, Abu Zuhayr, a Basran shaykh. Bukhari said, "Salt mentioned that he became confused." Muslim narrated from him, as did Musa Tabudhaki, and Ibn Adi mentioned him among the weak narrators. See Mizan (1/623). Abu Hatim said, "He is truthful."It appears that Ibn Abbas used to give rulings based on his own opinion, and had not heard anything about this matter from the Messenger of Allah ﷺ. He himself acknowledged this too, as in the hadith that follows.