By: Rabbi Mendel Weinbach
A Jew borrows a very expensive esrog from his neighbor to fulfill the mitzvah of taking the four species on Sukkos. Before he has a chance to return it, it somehow gets lost and he must now compensate the owner with another esrog. But why should he be required to purchase a similarly expensive esrog if he can provide him with a perfectly kosher one that is not of the same quality but much cheaper?
This question was dealt with by two great halachic authorities in connection with our Gemora (Bava Kamma 78) . The Sage Rava rules that if someone set aside an ox for fulfillment of his vow and that ox was stolen, the thief can replace it with a sheep and the victim cannot demand an ox because he wished to bring a sacrifice of greater quality. One opinion is that the case of the esrog is similar to this case and the ruling should be the same. A dissenting opinion is found, however, in the Responsa of Chacham Tzvi (Responsa 102). In the case of our Gemora, he points out, the thief did not cause his victim any loss of money, while he did so in the case of the esrog. That expensive esrog had the potential of being sold for a high price, while an animal set aside for sacrifice is not for sale.