When someone purchases it...

When someone purchases it, it is obligatory upon him to return it the original owner, if he is aware of him. When he is not aware of the original owner, he acts in accordance with whatever the Religious Authority has ordered (him to do). Issue 739: Consuming interest (Ribaa) is unlawful and it is of two types: First, the interest in loans whose discussion will come in the section of loans, with the permission of Allah, the Exalted. Second, interest in transactions.

It is to sell a commodity of a particular type, customarily sold by weight or volume, in return for a greater quantity of the same commodity. For example that a Mann (dry measure) of wheat is sold in…