Muhammad bin Mhbwb al-Binany محمد بن محبوب البناني · Commercial Transactions (Kitab Al-Buyu)

We were with the Messenger of Allah (ﷺ) at the battle of Khaibar. We were selling to the Jews one uqiyah of gold for one dinar. The narrators other than Qutaibah said: "for two or three dinars." Then both the versions agreed. The Messenger of Allah (ﷺ) said: Do not sell gold except with equal weight.