Mishkat al-Masabih 11 Business Transactions كتاب البيوع 53

وَعَنْ أَبِي سَعِيدٍ قَالَ: جَاءَ بِلَالٌ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِتَمْرٍ بَرْنِيٍّ فَقَالَ لَهُ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مِنْ أَيْنَ هَذَا؟» قَالَ: كَانَ عِنْدَنَا تَمْرٌ رَدِيءٌ فَبِعْتُ مِنْهُ صَاعَيْنِ بِصَاعٍ فَقَالَ: «أَوَّهْ عَيْنُ الرِّبَا عَيْنُ الرِّبَا لَا تَفْعَلْ وَلَكِنْ إِذَا أَرَدْتَ أَنْ تَشْتَرِيَ فَبِعِ التَّمرَ ببَيْعٍ آخر ثمَّ اشْتَرِ بِهِ»

Abu Sa’id said that Bilal brought the Prophet some barni * dates, and when he asked him where he had got them he replied, “I had some inferior dates, so I sold two sa’s of them for a sa .” He said, “Ah, the very essence of usury, the very essence of usury. Do not do so, but when you wish to buy, sell the dates in a separate transaction, then buy with what you get.” (Bukhari and Muslim.) * A type of dates of the best quality, sweet and luscious, red tinged with yellow.