Zayd bin Arqam and Bara bin Azib were business partners. They bought silver with both immediate and deferred payment. When this reached the Prophet ﷺ, he instructed them that whatever was paid for in cash was permissible, and whatever was on deferred payment must be returned.
إن زيد بن أرقم والبراء بن عازب كانا شريكين، فاشتريا فضة بنقد ونسيئة، فبلع ذلك النبي ﷺ، فأمرهما أن ما كان بنقد فأجيزوه، وما كان نسيئة فردوه.
Imam Ahmad narrated it (19307) from Yahya bin Abu Bukayr, who said, Ibrahim bin Nafi told us, I heard Amr bin Dinar mention from Abu Minhal, and he related the hadith. This is the sahih version of Abu Minhal's hadith, that the question concerned selling gold for silver with a difference in amount and on deferred payment. He permitted what was done hand to hand, and rejected what was on deferred payment, and this is what the jurists call sarf (currency exchange).As for what Humaydi narrated in his Musnad (2/317–318) from Sufyan bin Uyayna, from Amr bin Dinar, from Abu Minhal, who said, A partner of mine in Kufa sold dirhams for dirhams with a surplus between them, so I said, "I do not think this is proper." He said, "I sold it in the market, and no one criticized me for it." So I went to Bara bin Azib and asked him, and he said, "The Prophet ﷺ came to Madinah, and this was how we traded." He said, "Whatever is hand to hand, there is no harm in it, and whatever is on deferred payment is not good." "Go to Ibn Arqam, for he did more trading than I did." So I went to him and mentioned this to him, and he said, "Bara has spoken truly."Humaydi said, "This is abrogated, and it is not to be relied upon."Bayhaqi said, "This is a mistake, and the sahih version is what Ali bin Madini and Muhammad bin Hatim narrated, and this is what is meant by the unqualified wording in the narration of Ibn Jurayj, so the report concerns selling two different types of goods, one for the other." He said, "Whatever of it is hand to hand, there is no harm in it, and whatever of it is on deferred payment, there is not."