Sayyiduna Ubadah bin al-Samit (may Allah be pleased with him) stood and said: "O people! You have introduced transactions which I do not know. Gold for gold — its bullion and its coin — weight for weight, hand to hand in cash; and silver for silver, weight for weight, hand to hand in cash, and it is not right on credit. Wheat for wheat, mudd for mudd, hand to hand in cash; and barley for barley, mudd for mudd, hand to hand in cash. There is no harm in selling barley for wheat, with the barley being more, hand to hand in cash, but it is not right on credit. And dates for dates" — until he counted salt for salt — "like for like, hand to hand in cash. Whoever gives more or takes more has dealt in usury (riba)." Qatadah (may Allah have mercy on him) said: He was one who fought at Badr and attended al-Aqabah, one of the chiefs of the Ansar, who had pledged allegiance to the Messenger of Allah (peace and blessings be upon him) that he would not fear the blame of any blamer concerning Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10478