Sahih Al-Bukhari :: Book 3 :: Volume 34 :: Hadith 344
Narrated Az-Zuhri from Malik bin Aus:

that the latter said, “Who has change?” Talha said, “I (will have change) when our store-keeper comes from the forest.”

Narrated ‘Umar bin Al-Khattab: Allah’s Apostle said, “The bartering of gold for silver is Riba, (usury), except if it is from hand to hand and equal in amount, and wheat grain for wheat grain is usury except if it is form hand to hand and equal in amount, and dates for dates is usury except if it is from hand to hand and equal in amount, and barley for barley is usury except if it is from hand to hand and equal in amount.” (See Riba-Fadl in the glossary).

When one party gives something of value
and the other party pays him with something,
in this case paper, of no value,
and when one party’s wealth is created out of thin air,
while the other party has to slave and earn to pay off the ill-gotten credit or loan,
is this not devouring of other people’s wealth?

There is moreover a Hadith of Prophet Muhammed in the Sahih Muslim which teaches:
“Abu Said Al Khudri reported Allah’s messenger as saying:
“gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt. (When a transaction is) like for like, payment being made on the spot, then, if anyone gives more or asks more, he has dealt in riba, the receiver and the giver being equally guilty.”

This Hadith of Prophet Muhammed establishes two things:
ONE ‘money’ in Islam is either precious metals such as gold and silver, or commodities such as wheat, barley, dates and salt.
TWO when gold, silver, wheat, barley, dates and salt were used as money, their value was ‘inside’ and not ‘outside’ the money. Hence, it is established that ‘money’ in Islam must possess intrinsic value.
(Imran N. Hosein, “Explaining the Disappearance of Money with Intrinsic Value”, paper delivered at the International Conference on the Gold Dinar Economy, held in Kuala Lumpur on 24 and 25 July 2007, p. 1)