It was narrated that Mujahid said: Umar said: Dinar for Dinar, Dirham for Dirham, no difference between them, this is the obligation that our Prophet enjoined upon us.
It was narrated that Abu Hurairah said: The Messenger of Allah said: 'Gold for gold, weight for weight, like for like; and silver for silver, weight for weight, like for like. Whoever gives more or takes more has engaged in Riba. '