It was narrated that Malik bin Aws bin Hadathan said: "I came saying. 'Who will exchange Dirham?' Talhah bin 'Ubaidullah,
who was with 'Umar bin Khattab, said: 'Show us your gold, then Come to us; when our treasure comes, we will give you your silver: 'Umar said: 'No, by Allah, you will give him silver (now), or give him back his gold, for the Messenger of Allah P.B.U.H said: "Silver for gold is usury, unless it is exchanged on the spot.": (Sahih)