Abu al-Jawza' (may Allah have mercy on him) relates: We came to Sayyiduna Ibn Abbas (may Allah be pleased with them both), and he instructed us regarding bay' al-sarf (the exchange of gold and silver/currency). Then I visited him once, and he said: "We used to instruct you to do it, but now we forbid you from it." I said: What should we do about the (ruling) we have already given people? He said: "I met one of the Companions of the Messenger of Allah (peace and blessings be upon him) who had more knowledge of this matter than I do, and he forbade me from it, so I have forbidden you just as he forbade me."
No one narrated this hadith from Uqbah bin Abi Thubayt except Abu Hilal; and the elder whom Sayyiduna Ibn Abbas (may Allah be pleased with them both) met was Sayyiduna Abu Sa'id (may Allah be pleased with him).
Hadith Referenceالمعجم الأوسط / باب الميم / 6588
Hadith Takhrij«أخرجه ابن حجر فى «المطالب العالية» برقم: 1385، وعبد الرزاق فى «مصنفه» برقم: 14548، 14549، والطحاوي فى «شرح معاني الآثار» برقم: 5791، والطبراني فى «الكبير» برقم: 455»