In our Parashah appears the commandment to listen to the prophet: "A prophet from among your own people, like me, the Lord your God will raise up for you; you shall listen to him."¹ Regarding the words "you shall listen to him," our Sages of blessed memory² say: "Even if he says that one of all the mitzvot of the Torah should be transgressed, as Elijah did on Mount Carmel—always as something circumstantial—listen to him." The example of Elijah that our Sages bring up concerns the offering of sacrifices on altars outside the Temple in Jerusalem. Once the Holy Temple was built, the Jews were commanded to bring their sacrifices only to the altar of the Beit Hamikdash, prohibiting sacrifices on external altars, as had been the custom before. However, if a prophet indicates that a sacrifice should be made on an external altar, as an extraordinary instruction, as the prophet Elijah did on Mount Carmel, the commandment "you shall listen to him" applies, and it must be carried out.
EVERYTHING IS POSSIBLE
In light of this, a question that arises at the end of the Talmudic tractate Zevachim can be explained. There, the laws of offerings on external altars are detailed at length. But it is unclear: it is explicitly stated there that "they arrived in Jerusalem—the external altars were prohibited and were never again permitted." Given this, why do our sages teach us at length about something that no longer exists?.
We see from this that it is entirely possible for a sacrificial offering to be made on an external altar even today—if a prophet were to come and command it as an extraordinary instruction, just as the prophet Elijah did on Mount Carmel. In such a case, the command to heed the prophet's voice and offer on an external altar would fall upon us, and therefore we must know the rules for offering on an external altar.
PROPHECY TODAY
It is true that our Sages, of blessed memory, said: "Since the last prophets, Haggai, Zechariah, and Malachi, died, the Holy Spirit—ruach hakodesh—of Israel departed," and from this it would seem that prophecy is not possible today; however, this is not so. On several occasions, we find in the words of our Sages, of blessed memory, that the Holy Spirit—ruach hakodesh—also descended upon the Tzaddikim in times after the last prophets.
Also in the Rambam5 Law Code, in the laws of prophecy, there is no time limit for prophecy and it does not say that it is impossible to reach prophecy today.
Therefore, the words of our Sages, of blessed memory, "the Ruach HaKodesh departed from Israel," should not be interpreted as meaning that prophecy is no longer possible after the last prophets, but rather that it is not as common as it once was. This is also evident from analyzing the terms used here: it does not say "the Holy Spirit was annulled" or "interrupted," but "departed," since prophecy was not annulled or interrupted, but rather became something uncommon and difficult to access. However, the moment a person is found who meets the necessary requirements for prophecy to descend upon them—"the Holy Spirit immediately descends upon him," to use the language of Rambam.
THE SANCTITY OF THE SYNAGOGUE
The advantage of offering in the Holy Temple over offering on an external altar lies in the fact that when the sacrifice is offered in the Beit Hamikdash, the holiness also extends to the physical place where the altar is erected, making it a holy place as well.
This virtue remains relevant today, in the sanctity of the Beit Hamikneset—the synagogue—and the Beit Hamidrash—the House of Torah Study—which are a kind of "small sanctuary." Every good deed becomes more holy when performed in the synagogue; therefore, priority should be given to performing every sacred act in a Beit HaKneset, to add to the inherent holiness of the sacred act itself.
(Likutei Sichot Volume 14, Page 70)
NOTES: 1.Devarim 18:15 2.Yevamot 90,b 3.Yomah 9,b Sotá 48,b 4.See Pirkei Guiluim of Rabbi Margaliot. 5. Hilchot Yesodei HaTorah Ch. 4