(15) باب الصَّرْفِ وَبَيْعِ الذَّهَبِ بِالْوَرِقِ نَقْدًا
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.
Reference: Sahih Muslim 1588 a
In-book reference: Book 22, Hadith 105
USC-MSA web (English) reference(deprecated numbering scheme): Book 10, Hadith 3856