Mukhtasar Muslim

Malik bin Aws bin Hadthan narrates: He says, "I came saying, 'Who will exchange silver for gold?' Sayyiduna Talha bin Ubaidullah said—and he was sitting with Sayyiduna Umar bin Khattab (may Allah be pleased with him)—'Give me your gold, then come back after a while. When our servant comes, we will give you your price.' Sayyiduna Umar (may Allah be pleased with him) said, 'Never! Either give him his silver at that very moment or return his gold to him. Because the Messenger of Allah (peace and blessings be upon him) said: Exchanging silver for gold is usury, except when it is hand to hand; and exchanging wheat for wheat is usury, except when it is hand to hand; and exchanging barley for barley is usury, except when it is hand to hand; and exchanging dates for dates is usury, except when it is hand to hand.'"