Sayyiduna Ma'mar (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Food for food must be equal for equal."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10515
Sayyiduna Abdullah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) "cursed the one who gives usury and the one who consumes it." The narrator said: I said: And its two witnesses and its writers too? He said: We narrate only what we heard.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10516
Nafi' narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) "forbade selling the fruit on the date palms for dried dates by measure, raisins for grapes by measure, and standing crops for wheat by measure."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10517