What is the ruling on selling types of herbal remedies (such as harmal, and bakhour from the horn of a rhinoceros, and Jawi) to individuals known to be sorcerers or magicians who use them for illusory purposes?

If you know that the buyer will use the goods for unlawful purposes such as sorcery or divination, then it is not permissible for you to sell them to him, as this constitutes cooperation in sin and transgression. However, if he will use them for permissible purposes, or if you do not know his circumstances, then it is permissible to sell them to him, unless the predominant use of these goods is unlawful.