Sayyiduna Ubadah bin Samit (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Gold for gold, silver for silver, dates for dates, wheat for wheat, barley for barley, and salt for salt must be equal in amount and hand to hand. If these types differ, then sell as you wish, provided it is hand to hand (on the spot)."