forbade breaking any of the Muslims’ coinage circulating among them unless it was defective.
One of the early Muslims said, “Breaking the Muslims’ coinage is a form of corruption in the land.”
It has also been said that this was among the things for which Allah—majestic is His glory—condemned the people of Shuayb, when He said: “Do not deprive people of what is theirs, and do not spread corruption in the land.” [Hūd: 85]
It is, however, permissible to break debased coinage, for if people were permitted to deal in it, the extent of its debasement would not be apparent. Al-Hasan narrated from the Prophet—peace and blessings be upon him—that he forbade diluting milk with water for sale (1). This means that milk may be mixed with water for drinking, but it may not be sold that way, even if the buyer knows that it has been diluted, because the extent of the dilution is not apparent.
Among the gravest forms of fraud is alchemy (2): the production of substances resembling gold and silver. Likewise, imitations are made of gemstones and aromatic substances such as musk, saffron, ambergris, and others. The meaning of alchemy is imitation. All of this is forbidden, for something manufactured can never be identical to something created; at most, it can be made to resemble it outwardly and in some of its qualities.