Messenger of Allah ﷺ appointed somebody as a governor of Khaibar. That governor brought to him an excellent kind of dates (from Khaibar). The Prophet ﷺ asked, "Are all the dates of Khaibar like this?" He replied, "By Allah, no, O Messenger of Allah ﷺ! But we barter one Sa of this (type of dates) for two Sas of dates of ours and two Sas of it for three of ours." Messenger of Allah ﷺ said, "Do not do so (as that is a kind of usury) but sell the mixed dates (of inferior quality) for money, and then buy good dates with that money."  

أَنَّ رَسُولَ اللَّهِ ﷺ اسْتَعْمَلَ رَجُلاً عَلَى خَيْبَرَ فَجَاءَهُ بِتَمْرٍ جَنِيبٍ فَقَالَ رَسُولُ اللَّهِ ﷺ أَكُلُّ تَمْرِ خَيْبَرَ هَكَذَا قَالَ لاَ وَاللَّهِ يَا رَسُولَ اللَّهِ إِنَّا لَنَأْخُذُ الصَّاعَ مِنْ هَذَا بِالصَّاعَيْنِ وَالصَّاعَيْنِ بِالثَّلاَثَةِ فَقَالَ رَسُولُ اللَّهِ ﷺ لاَ تَفْعَلْ بِعِ الْجَمْعَ بِالدَّرَاهِمِ ثُمَّ ابْتَعْ بِالدَّرَاهِمِ جَنِيبًا