The Rishonim disagree regarding a food item that the Gemora is uncertain if it is forbidden or not and it remains unresolved. The inquiry will remain in that state until Eliyahu Hanavi clarifies it for us. The Ohr Zarua maintains that this is regarded as “something which can become permitted,” since there is a possibility that Eliyahu will say that it is permitted. The Rashba disagrees and he explains: If Eliyahu will decide that the food is forbidden, it will emerge that this item will never be permitted. If he will rule that it is permitted, it actually was never forbidden. Either way, he argues, it cannot be labeled as “something which can become permitted.” The Bach cites a Mordechai that it is not considered “something which can become permitted,” for by the time Eliyahu will permit it, the food will be already ruined.

The Chasam Sofer cites the following question from the Rav in Frankfurt: Chazal write that a pig is called a “chazir,” for in the future, Hashem will reverse the prohibition of the pig and it will be permitted. If so, according to those Rishonim, pig should be regarded as “something which can become permitted”?

The Chasam Sofer answers based upon that which was written in the Toldos Yitzchak: The Torah forbids animals that do not have split hooves, or those that do not chew their cud because those animals are naturally conceited; they trample with their feet and they have a poison inside of them, which is extremely dangerous for a Jew to eat. The animals that do not digest their food easily and they are compelled to chew their cud; those animals are permitted to eat.

If so, explains the Chasam Sofer, there will be no change in halacha regarding the pig. It was forbidden and will remain forbidden. Rather, Hashem will change the nature of the pig and it will begin to chew its cud. That is why it will be permitted then. Accordingly, the only pigs that will be permitted then, are those that will be born after this change occurs; however, the pigs that were in existence prior to that will remain forbidden. This is why a pig is not classified as “something which can become permitted.”