Dealing with Forbidden Goods
1. We are prohibited to do business with or accept as collateral any
substance which the Torah forbids one to eat, even though we are permitted
to benefit from it. It is even forbidden to but it with the intention of
feeding it to a non-Jew.
However, one may trade in forbidden articles which are not prepared to be
eaten - e.g., horses or donkeys. Non-kosher fat may also be sold, for
[Leviticus 7:24 explicitly] states: "It may be used for any other service."
2. Nevertheless, if, by chance, a person comes into possession of a
forbidden article - e.g., he was fishing and unintentionally caught a
non-kosher fish, or one of his animals died or was attacked - he may sell
it, since he did not intend to possess it. However, he must sell it
immediately, without waiting for it to fatten in his possession.
Similarly, he is allowed to sell [a forbidden article acquired
unintentionally], using [a Jewish] agent, even though the agent will also
make a profit. However, the agent may not buy the article outright, since
that would be considered as if he were doing business with non-kosher items.
3. Similarly, it is permissible to accept non-kosher food items as payment
for debts, provided they are sold immediately. It is forbidden to maintain
possession of them in the hope of making a profit. Nevertheless, one may
hold them in one's possession to avoid suffering a loss.
4. Foods which are forbidden only because of Rabbinic decree - e.g.,
non-Jewish cheese - may be purchased for trade.