Sayyiduna Umar bin Al-Khattab (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "When selling gold for gold, it must be hand to hand (not on credit), likewise, when selling silver for silver, it must be hand to hand, and dates for dates must be hand to hand, and wheat for wheat must be hand to hand, and barley for barley must be hand to hand, and there should be no increase or decrease among these (commodities)."