The Messenger of Allah ﷺ said, "Dates for dates, wheat for wheat, barley for barley, and salt for salt, like for like, hand to hand. Whoever gives more or asks for more has dealt in usury, except when the kinds differ."
قال رسول الله ﷺ: التمر بالتمر، والحنطة بالحنطة، والشعير بالشعير، والملح بالملح مثلا بمثل، يدا بيد. فمن زاد أو استزاد فقد أربى إلا ما اختلفت ألوانه.
Muslim narrated it in "Musaqah" (1588:83) via Ibn Fudayl bin Ghazwan, from his father, from Abu Zura, from Abu Hurairah, and he mentioned it.His statement, "its colors," means its varieties.