According to a story related in the Midrash, the scenario of the Holy Temple being rebuilt even before Moshiach's revelation is entirely possible. The story took place in the days of Rabbi Joshua ben Chananiah, a short time after the destruction of the Second Temple. The Roman Empire had instructed the Jews to rebuild the Temple, and plans got underway, even though Moshiach had not appeared. In the end, the plans were cancelled because of the interference of some nefarious elements. However, the fact that the sages were prepared to rebuild the Holy Temple even in the absence of Moshiach indicates that the matter is not out of the question.

This conclusion can also be reached from the words of the Jerusalem Talmud, which states that the Jewish exiles will rebuild the Holy Temple, without attributing this act to Moshiach.

However, Maimonides rules halachically that only Moshiach will rebuild the Holy Temple. How do we reconcile his ruling with the abovementioned story and the statement of the Jerusalem Talmud?

The Lubavitcher Rebbe answers that Maimonides' ruling also has a source in the words of our sages. On a verse in the Song of Songs: "Awaken, North, and come south," Rabbi Elazar expounds that Moshiach is found together with the Jewish People since they were exiled to the north, to Babylonia and Rome. "When Moshiach, who is in the north, in exile, will awaken, he will come and build the Holy Temple in the south"--in Jerusalem, which is in the southern part of Israel. This provides evidence that Moshiach will rebuild the Temple.

Why does Maimonides accept the interpretation of Rabbi Elazar over the event that happened in the days of Rabbi Joshua ben Chanania? The Lubavitcher Rebbe explains that Rabbi Elazar lived in a later period than Rabbi Joshua. In the times of Rabbi Joshua, the sages accepted the fact that the Temple could be rebuilt even without Moshiach. However, by the time of Rabbi Elazar, it had become the established view amongst the sages that only Moshiach would rebuild the Temple, and this is the halachic ruling that is valid for today.

(Jerusalem Talmud, Megillah, ch. 1:11. Pesachim 9:1. Bereishis Rabbah, 64. Vayikra Rabba 9:6. Likuttei Sichos, vol. 27, p. 204, footnote 96)