Sale of the prohibited

In the forty-fifth hadith of Ibn Rajab's additions, the prohibition of selling forbidden things: "God and His Messenger have forbidden the sale of wine, carrion, pork, and idols." What is forbidden to eat or to benefit from in its own form is therefore forbidden to sell. He takes the extension of the prohibition to its price from the story of the animal fat of carrion, about which the questioner asked whether it could be used for pitch, oil, and lighting, and the reply was "No, it is forbidden"; and from the words "God curse the Jews, for God forbade them fat, so they melted it, sold it, and ate its price." The rule is that what is forbidden in its substance is forbidden in its price, and changing its form does not make it lawful. ¹ (Jami al-ulum wal-hikam, p. 871)

What is not recorded here needs a further source.