Musnad Ahmad Hadith 11479

Abu Al-Jawza says that I asked Ibn Abbas (may Allah be pleased with him) about buying and selling gold and silver with an increase or decrease, but in cash, so he said that there is no harm if it is two for one or with an increase or decrease, as long as it is in cash. After some time, I was again blessed with the opportunity to perform Hajj, and Ibn Abbas (may Allah be pleased with him) was still alive at that time. I asked him the same question again, so he said that with cash, the weight of both should also be equal. I said to him that earlier you gave me the fatwa that even two for one is permissible, and since then I have been telling people the same ruling. He said that was my opinion; later, Abu Saeed Khudri (may Allah be pleased with him) narrated this hadith to me, so I abandoned my opinion in favor of the hadith.