The three wells dug by Yitzchak.
According to Ramban, the three wells dug by Yitzchak allude to the three Holy Temples. The analogy of digging a well precisely describes the process of building the Temple: First there is a phase of intense physical effort to dig the well, followed by the actual filling of the well with water which does not require any direct effort, it simply floods in. Similarly, the building of the Temple requires tremendous human effort, but the indwelling of the Shechinah (Divine Presence)—which is the very purpose of building the Temple—is an effortless consequence of the Temple’s construction
This analogy appears to break down, however, in the case of the Third Temple which, according to the Zohar (III 221a), will be built by God, and not by man. It seems at first glance that Ramban’s analogy for the Third temple of digging a well is inappropriate.
However, even according to the Zohar, the Third Temple is built through human effort too. Not through the physical effort of working with stones and mortar, but rather, by the dedicated acts of supra-rational mitzvah observance by Jewish people, in defiance of the challenges of exile. The cumulative effects of these acts are thus described by the Zohar as a “building made by God,” though in fact, it is a building made by human mitzvah acts that are totally dedicated to God.
Thus, the building process of the Third Temple consists of mitzvos perform ed out of simple obedience to God. Therefore, they are eternal.
(Based on Likutei Sichos vol. 30, p.116ff.)