Sunan Ibn Majah Book 12, Hadith 2256

حَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا عَبْدَةُ بْنُ سُلَيْمَانَ، عَنْ مُحَمَّدِ بْنِ عَمْرٍو، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي سَعِيدٍ، قَالَ كَانَ النَّبِيُّ ـ صلى الله عليه وسلم ـ يَرْزُقُنَا تَمْرًا مِنْ تَمْرِ الْجَمْعِ فَنَسْتَبْدِلُ بِهِ تَمْرًا هُوَ أَطْيَبُ مِنْهُ وَنَزِيدُ فِي السِّعْرِ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏ "‏ لاَ يَصْلُحُ صَاعُ تَمْرٍ بِصَاعَيْنِ وَلاَ دِرْهَمٌ بِدِرْهَمَيْنِ وَالدِّرْهَمُ بِالدِّرْهَمِ وَالدِّينَارُ بِالدِّينَارِ لاَ فَضْلَ بَيْنَهُمَا إِلاَّ وَزْنًا ‏"‏ ‏.‏

It was narrated that Abu Sa’eed said:“The Prophet used to give us dates from the collection (mixed) [1] dates, and we would exchange them for dates that were better, and we add to the price. [2] The Messenger of Allah said: ‘It is not right to give one Sa of dates for two Sa, nor one Dirham for two Dirham. A Dirham for a Dirham and a Dinar for a Dinar is allowed: the only difference between them is in weight (i.e., the weight must be equal.)’” Sahih