Bava Kama 78b: Rava asked: If a man vowed to bring an olah, and set aside an ox, and someone stole it, can the thief make restitution with a sheep (or a bird according to Rabbi Elazar ben Azariah who holds that one making a vow without specifying the size of the animal can use a bird)? Do we focus on the vow which was to bring any olah, or can he demand an ox on the grounds that he wishes to perform the mitzvah in the best way? Rava answered his own question: He may make restitution with a sheep or a bird.
בבא קמא עח ע”ב: בעי רבא: הרי עלי עולה והפריש שור, ובא אחר וגנב, מי פטר גנב נפשיה בכבש לרבנן, בעולת העוף לר׳ אלעזר בן עזריה? דתנן: הרי עלי עולה ־ יביא כבש, ר״א בן עזריה אומר: יביא תור או בן יונה, מאי? מי אמרינן שם עולה קביל עילויה, או דלמא מצי א״ל אנא מצוה מן המובחר בעינא למיעבד? בתר דאיבעיא הדר פשט: גנב פטר עצמו בכבש לרבנן, בעולת העוף לר׳ אלעזר בן עזריה.
In 1903, Rabbi Elchonon Wasserman began his first position as rosh yeshiva in Mtsislavl. One of his talmidim from that period, Rabbi Shmaryahu Nochum Shushenkin, kept a diary in which he described Reb Elchonon’s teaching method. “It was Reb Elchonon’s practice to stop delivering his shiur for a day or two after the completion of a Perek, or half a Perek, if it was lengthy, to allow the students to review what they had learned so far. For this he would organize groups of four or five students with similar abilities. Because of his erudition in the writings of the Acharonim, he was capable of sharpening and testing his students by means of an interesting device. He would pose questions to them which had been answered by the Acharonim, for instance Noda Beyehuda, Rabbi Akiva Eiger, Chasam Sofer and others, by reference to the Gemara or Tosafos which the pupils had been studying. If the Gemara or Tosafos had been thoroughly assimilated and retained in the student’s mind, he would discover the answer to Reb Elchonon’s questions in the Gemara he had been studying that day or the day before.
“I remember one question posed to us by Reb Elchonon. Someone had stolen an esrog of superior quality. Could he make restitution by giving the owner a kosher, but not so beautiful esrog? We found the answer in Rava’s remark in Merubah. There the case is mentioned of someone who had vowed to bring a korban olah and had set aside an ox for the fulfillment of his vow. A thief stole the ox. According to the Sages, the thief can free himself from further obligation by restoring a sheep, and according to Rabbi Elazar ben Azariah, even by a bird suitable for a korban olah. Similarly in our case, the thief may free himself of further obligation by restoring an esrog of inferior quality, as long as it is kosher. The plaintiff’s argument – “I want to perform a mitzvah in the most elegant manner” – has no validity.
Source; Reb Elchonon (Artscroll), p. 41
[The comparison between a korban and an esrog is surprising. A korban does not belong to the vower, and the thief is only paying because of Rabbi Shimon’s rule that דבר הגורם לממון כממון דמי (something that causes you to lose money is like your money), as Rashi says. Since if the thief were not caught, the vower would only have to bring a sheep to replace the ox, the thief too need only pay for a sheep. But an esrog is not consecrated to hekdesh, and it is the regular property of the owner. How then can a thief make restitution with something worth less than what he stole?
It seems that Reb Elchonon was saying a tremendous chiddush here: an esrog is not intrinsically worth the amount of money you pay for it. It is valuable only as a דבר הגורם לממון, and is therefore only worth the amount that you would have to pay to do the mitzvah at the simplest level.
Of course, this would only apply to the person planning to use the esrog for the mitzvah on Succos, not to a merchant. Thus a thief who stole a $100 esrog from an esrog store could not make restitution with a $50 esrog. (See the article “Purloined Esrogim” by Rabbi Meir Orlian of the Business Halacha Institute, in which someone stole expensive esrogim from a merchant before Succos and returned them after Succos. The psak there was that he must pay their full pre-Succos value.)
The Chazon Ish (Bava Kama 6:3) similarly rules that if someone damages a person’s house, the amount he pays would depend on what the owner intends on doing with the house. If he plans to fix the damage, he would pay the cost to fix it, but if he plans to sell it, he would only pay the negligible amount by which the house dropped in value.
However, the Chazon Ish there quotes a Rashi that seems to contradict all of the above. Rashi in Gittin 53a says that if kohanim ruin a korban through pigul, they have to pay even if the korban was a nedavah, an optional korban for which the owner is not responsible if lost. Even though they didn’t cause the owner any loss, he can argue that he wanted to bring his korban and thus suffered a loss. How does this fit with Reb Elchonon, and indeed, with the Gemara we began with in Bava Kama 78b? Maybe Rashi means that he will not replace the korban at all, so he is demanding compensation for his disappointment at not bringing any korban. In our case, however, he is replacing the korban (or esrog), albeit with a less expensive one.
As an aside, we can learn from Reb Elchonon the great value of analyzing stories and real life cases in order to better understand the Gemara.]