As for the objection:

“How could the dirham undergo a change and become unlawful through a prohibited means, yet not undergo a change and become lawful through a legitimate means?”

The answer is: Rather, change does occur in what is prohibited because of its properties, not in what is prohibited because of how it was acquired.

The first is exemplified by wine: when it was juice, it did not become lawful and pure; once it fermented, it became unlawful and impure. If it then turns into vinegar by Allah’s action, without any deliberate attempt to turn it into vinegar, it becomes wine vinegar that is lawful and pure, by scholarly consensus. They disagree only when someone deliberately seeks to turn it into vinegar. They also disagree concerning other impure substances, such as a pig that turns into salt or an impure substance that turns into ash. One view is that it does not become pure. This is the position of al-Shāfi‘ī and one of the two positions within the schools of Mālik and Ahmad.

The “second” is exemplified by usurped property. It is unlawful because it was taken unjustly; if it is taken rightfully, it becomes permissible. For example, the owner may consent to the usurper’s possession of it, give it to him as a gift, or sell it to him; or the owner, his guardian, or his agent may take possession of it. Furthermore, if the usurper gives it to someone who does not know that it was usurped, that person’s receipt of it is rightful, for Allah does not hold him responsible for what he does not know. Likewise, he explained that his receipt of it from the recipient was rightful. Liability has already been discussed. And Allah knows best.