Hadith 523
Sayyiduna Umar bin Khattab (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) said: "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and raisins for raisins must be equal, and salt for salt must be hand to hand. Whoever gives more or takes more has engaged in usury."