The Prophet of Allah (sws) is reported to have said:
If you sell gold on credit, take back gold of the same
type and the same quantity; and if you sell silver on credit, take back silver
of the same type and the same quantity; for he who gave more or desired more,
then this is precisely what Ribā is. (Muslim, Kitābu’l Buyū‘)
If you sell silver on credit in exchange for gold there is
the possibility of Ribā in it.
Similarly wheat in exchange for wheat of another type, barley in exchange for
barley of another type, dates for dates of another type.
However, if the exchange is done on the spot, then there is no harm in it. (Muslim, Kitābu’l Buyū‘)
These directives are meant to prevent Ribā from creeping
into barter on credit through the back door. It is obvious from these directives
that the Prophet (sws) wanted his followers to refrain even from the traces of