[Machine] "I had a container of dates with me for the Prophet ﷺ, but I found a better quality of dates, twice as much for the same price, so I bought them. Then I went to the Prophet ﷺ and he asked me, 'Where did you get these, O Bilal?' I replied, 'I bought a container of dates for the same price as what we had.' He said, 'Return it and bring back the dates we had.'"  

كَانَ عِنْدِي مُدُّ تَمْرٍ لِلنَّبِيِّ ﷺ فَوَجَدْتُ أَطْيَبَ مِنْهُ صَاعًا بِصَاعَيْنِ فَاشْتَرَيْتُ مِنْهُ فَأَتَيْتُ بِهِ النَّبِيَّ ﷺ فَقَالَ «مِنْ أَيْنَ لَكَ هَذَا يَا بِلَالُ؟» قُلْتُ اشْتَرَيْتُ صَاعًا بِصَاعَيْنِ قَالَ «رُدَّهُ وَرُدَّ عَلَيْنَا تَمْرَنَا»  

Messenger of Allah ﷺ sent the brother of the tribe of Bani Adi Al-Ansari as governor of Khaibar. Then the man returned, bringing Janib (a good kind of date). Messenger of Allah ﷺ asked him, "Are all the dates of Khaibar like that?" He replied, "No, by Allah, O Messenger of Allah ﷺ! We take one Sa' of these (good) dates for two Sas of mixed dates." Messenger of Allah ﷺ then said, "Do not do so. You should either take one Sa of this (kind) for one Sa' of the other; or sell one kind and then buy with its price the other kind (of dates), and you should do the same in weighing." (Using translation from Bukhārī 7350)  

أَنَّ أَبَا سَعِيدٍ الْخُدْرِيَّ وَأَبَا هُرَيْرَةَ حَدَّثَاهُ أَنَّ رَسُولَ اللَّهِ ﷺ بَعَثَ أَخَا بَنِي عَدِيٍّ الْأَنْصَارِيَّ فَاسْتَعْمَلَهُ عَلَى خَيْبَرَ فَقَدِمَ بِتَمْرٍ جَنِيبٍ قَالَ ابْنُ مَسْلَمَةَ يَعْنِي جَيِّدًا فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ «أَكُلُّ تَمْرِ خَيْبَرَ هَكَذَا؟» قَالَ لَا وَاللَّهِ يَا رَسُولَ اللَّهِ إِنَّا لَنَشْتَرِي الصَّاعَ بِالصَّاعَيْنِ مِنَ الْجَمْعِ فَقَالَ رَسُولُ اللَّهِ ﷺ «لَا تَفْعَلُوا وَلَكِنْ مِثْلًا بِمِثْلٍ أَوْ بِيعُوا هَذَا وَاشْتَرُوا بِثَمَنِهِ مِنْ هَذَا وَكَذَلِكَ الْمِيزَانُ»