كتاب المساقاة
22  
The Book of Musaqah
(15)
Chapter: Exchange and Selling Gold for Silver on the spot
(15)
باب الصَّرْفِ وَبَيْعِ الذَّهَبِ بِالْوَرِقِ نَقْدًا ‏‏
Sahih Muslim 1588 a

Abu Huraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:

Dates are to be paid for by dates, wheat by wheat, barley by barley, salt by salt, like for like, payment being made on the spot. He who made an addition or demanded an addition, in fact, dealt in usury except in case where their classes differ.
حَدَّثَنَا أَبُو كُرَيْبٍ، مُحَمَّدُ بْنُ الْعَلاَءِ وَوَاصِلُ بْنُ عَبْدِ الأَعْلَى قَالاَ حَدَّثَنَا ابْنُ فُضَيْلٍ، عَنْ أَبِيهِ، عَنْ أَبِي زُرْعَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ التَّمْرُ بِالتَّمْرِ وَالْحِنْطَةُ بِالْحِنْطَةِ وَالشَّعِيرُ بِالشَّعِيرِ وَالْمِلْحُ بِالْمِلْحِ مِثْلاً بِمِثْلٍ يَدًا بِيَدٍ فَمَنْ زَادَ أَوِ اسْتَزَادَ فَقَدْ أَرْبَى إِلاَّ مَا اخْتَلَفَتْ أَلْوَانُهُ ‏"‏ ‏.‏
Reference : Sahih Muslim 1588a
In-book reference : Book 22, Hadith 105
USC-MSA web (English) reference : Book 10, Hadith 3856
  (deprecated numbering scheme)