There is a custom is to invite one of the historic leaders of the Jewish People on each of the seven days of Sukkot — namely, Abraham, Isaac, Jacob, Moses, Aaron, Joseph, and David. The prophet refers to these seven ushpizin (guests): “We shall raise against him seven shepherds and eight princes of men” (Micah 5:4). They are called the “seven shepherds,” for they shepherd Israel as a shepherd leads his flock.  What is the connection between these figures and the Sukkot festival in particular?
The seven “shepherds,” seven eminent historical leaders of Israel, are distinguished from the other leaders of Israel in that they do not belong to history alone (although they certainly influenced history). These leaders are above history in that they have continued to lead the Jewish People throughout the generations, even in our own times. We sense that they are present among us not as memories from the past, but as direct influences on each of our souls.
The shepherds are our forefathers, the forebearers of all the souls of Israel. Regardless of whether they are our biological forefathers, like the three Patriarchs, or our spiritual forefathers, as in the case of Joseph and David, we bear a part of their essence within ourselves. They are not external figures; but rather, they form our inner essence.
On Sukkot, the “Festival of the Ingathering,” we gather together all the separate parts of existence. It is a festival of reconciliation, peace and culmination, in which everything is put in its place — the reunification of existence.
When we sit in the shade of the sukkah, “in the shelter of the Most High” (Psalms 91:1), we invite ourselves to receive the ushpizin, who are a part of ourselves. For the sake of this invitation, we must go out to a place that is outside of civilization, outside the usual order of life. There, we build ourselves a temporary structure and cover it in shade, under the lofty hand of God, which protects and shelters us: “I have sheltered you with My hand” (Isaiah 51:16). There we meet ourselves — not as we are throughout the year, but as we are together with our forefathers, in the ideal form of what we are in essence.
On this festival, as all the ushpizin assemble, we should be willing to receive them, to integrate within ourselves all these parts of our being. We open the door and invite them, one by one, to enter and give all that they have to give. We invite them to the sukkah, to enter together with us into the source, into the place that includes us all (or, as it says in Sukkah 27b, “All of Israel are able to sit in one sukkah”).
The people of Israel provide sustenance for their Father in Heaven
The “seven shepherds” are so called because they provide guidance and sustenance, just as a shepherd guides and provides sustenance for his flock. On a simple level, the “flock” that they shepherd consists of the souls of Israel; the “seven shepherds” guide and nourish the souls’ spiritual faculties. The “seven shepherds” are leaders of the Jewish People, who guide the people and show them the way they are to go; they nourish the souls of Israel with Torah and mitzvot and with insight into divinity (a number of sources explain that the Torah is the soul’s nourishment and the mitzvot are the soul’s garments).
However, the “shepherds” have an additional significance as well. God refers to the community of Israel as “My brothers and friends (rei’ay)” (Psalms 122:8) and as “My sister, My love (ra’ayati)” (Song of Songs 5:2). The people of Israel are God’s rei’a, God’s “friend”, in the sense that they are His ro’eh His shepherd. The community of Israel shepherds and nourishes God, as it were. As our Sages put it, “The people of Israel provide sustenance for their Father in Heaven” (Zohar III, 7b).
In order to understand this astounding statement, one must conceive of “sustenance” in the broadest sense. Sustenance means nourishment, to feed in order to keep body and soul together. When a person does not eat, the soul is gradually separated from the body — first there is impairment of the soul’s ability to think, walk and act, until finally there is complete separation — death. Conversely, when a person eats, he strengthens the connection between his body and soul; when a person nourishes and provides sustenance to someone else, he keeps that person’s soul in his body.
This is true in the macrocosm as well. The universe is like a body, and God is like its soul. Thus, building and strengthening the connection between God and the world is conceived of as sustenance, and those who serve God and reveal His presence in the world “shepherd” and nourish Him, as it were. This does not mean that without our service, God would cease to exist; rather, it means that without our service, He cannot be expressed. His presence would not be felt in the world.
This hyperbolic conception appears in a different manner in an interpretation by our Sages commenting on the verse “You are My witnesses . . . and I am God” (Isaiah 43:12): “As long as you are My witnesses, I am God; but if you do not attest to Me, then I, as it were, am not God.” (The Midrash on Psalms, 123).
By definition, a witness is not simply someone who saw something, but someone who can also recount it, someone who by virtue of his testimony has attained a new awareness and is able to express it. Our task as shepherds, as witnesses, is to maintain God’s presence in the world. Without our worship, without our efforts and self-devotion, God is, as it were, not present in the world.
The two aspects of shepherds — shepherding the souls of Israel and sustaining God — are interrelated. The seven shepherds nourish the people of Israel with spiritual faculties through which “the people of Israel provide sustenance for their Father in Heaven;” Abraham nourishes them with love, Isaac with awe, Moses with knowledge, and so forth. In other words, the shepherds, as it were, shepherd God through the souls of Israel – by means of the seven spiritual faculties that they cultivate in Israel and through which the people of Israel serve God.
Princes of men
In addition to the “seven shepherds,” the prophet also refers to the “eight princes of men” — Jesse, Saul, Samuel, Amos, Zephaniah, Zedekiah, the Messiah, and Elijah (Sukkah 52b). Although they too influence the souls of Israel in every generation, these leaders are not shepherds; their relationship to the community of Israel is of a different nature. The shepherds’ guidance penetrates and becomes an intrinsic part of the souls of Israel. The one who leads and the one who is led are thus no longer two different figures; rather, they are unified and become, in essence, one. By contrast, the influence of the princes does not penetrate the soul’s faculties; it surrounds and envelops the soul.
The first of these two types of influence becomes, consciously or unconsciously, part of one’s inner being, part of one’s consciousness and emotional life. The second type of influence, that of the princes, always operates from without. It changes not one’s inner being, but the general climate, the surrounding atmosphere.
All of the “princes” were prophets sent by God to direct Israel, with the exception of one. Jesse, David’s father, acted on his own, without holding any public office of any kind. Officially, his words and actions had no binding force on other people. Nevertheless, he and the other “princes of men” influence the world by their very existence. Because they exist, the world in which they live is no longer the same. Perhaps nothing specific has changed, but, rather, the world as a whole is a different world.
A person may be a teacher and leader, and thereby influences the world; but there are others influence the world not by what they say or do, but by the fact that they exist. This is “surrounding,” indirect influence.
By way of analogy, these two types of influence can be compared to the effects of electromagnetic forces and the force of gravity. While heat and electricity create effects by sending waves out to an object, gravity affects the object simply because of its very existence. Because gravity exists, it has an effect; nothing can escape it.
Thus, we find the Messiah among the “eight princes of men.” Even though the Messiah never existed in the world and never acted in it, the very belief in the coming of the Messiah is a motivating force, our world looks different because we expect him. Hence, the Messiah is not a prince of the present, but a prince of the future.
Festival of joinings
The dual influence, surrounding and inner, characterizes everything connected with the Festival of Sukkot. The seven shepherds relate to the eight princes of men in the same way as the seven days of Sukkot (“You shall dwell in sukkot seven days”) are connected to the eighth day of Shemini Atzeret. In fact, the same relationship exists between the mitzvah of dwelling in the sukkah and the mitzvah of taking the lulav.
We take the lulav and the etrog in our hands and shake them; we form a direct, inner relationship with them. In contrast, we need not form any relationship with the sukkah; we exist inside it, and as a result of our very presence. It influences us by its existence around us. When we take the lulav in the sukkah, we join the surrounding influence with the inner influence. 
Similarly, when we invite the seven shepherds into the sukkah in which we are enveloped during the Festival of Sukkot, we join their inner influence with the surrounding influence of the Clouds of Glory.
 Some of the “shepherds” were, at an early stage in their lives, actually herdsmen. As our Sages say of Moses, and similarly of King David, “God said, ‘Let the one who is skilled as a shepherd of the flock…come and shepherd My people’” (See Shemot Rabbah 2:2, 4).
 “As God fills the whole world, so the soul fills the whole world. As God sees but is not seen, so the soul sees but is not seen. As God nourishes the whole world, so the soul nourishes the entire body. As God is pure, so the soul is pure. As God dwells in the innermost recesses of the universe, so the soul dwells in the innermost recesses of the body” (Berakhot 10a).
 Torah Or 33c: “The explanation of the matter is as follows. Ro’eh has two meanings: (a) one who sustains others, as in ‘nourish us (re’einu), feed us’; (b) one who nourishes himself, as in ‘the she-asses were grazing (ro’ot) alongside them’ . . . So, too, in the case of the seven shepherds (ro’im), both these elements are present, for they nourish the community of Israel.”
 So, too, Aaron. Likkutei Torah, Bamidbar 29c: “As it is written, ‘The soul of man is the lamp of God.’ The community of Israel’s souls is called ‘menorah.’ [This menorah] bears seven lamps, corresponding to seven levels in Divine service . . . Now, it is Aaron who kindles these lamps, for he is one of the seven shepherds who cause vitality and Godliness to flow to the community of Israel’s souls . . .”
 See Torah Or 34a: “The distinction between the shepherds and the princes of men can be better understood in light of the following. Rabbi Yohanan b. Zakkai was the great master of Torah, the Torah teacher of the entire nation, and yet he said to Rabbi Hanina b. Dosa, ‘Ask for mercy on my behalf,’ for [the power of] Rabbi Hanina’s prayer exceeded his own . . . Now, we do not find that Rabbi Hanina b. Dosa approached the stature of Rabbi Yohanan b. Zakkai as a teacher of Torah, nor do we find laws attributed to him in the Mishnah. The explanation of this matter lies in the difference between the shepherds and the princes of men . . . For Rabbi Yohanan b. Zakkai shepherded and sustained Israel, like Moses, whereas Rabbi Hanina b. Dosa lacked this dimension; but he was a perfect tzaddik, unblemished, so that our Sages said that the world to come was created solely for his sake, and from him the souls of Israel received the ways of [Divine] service and piety…”
 Siddur Admor ha-Zaken, sha’ar ha-lulav, 265a: “This would also explain why the lulav should be taken precisely in the sukkah. For the root meaning of the mitzvah of the sukkah roof and of the mitzvah of taking the lulav is the same, only that via the roof the light is drawn as surrounding light, whereas via the lulav it is drawn as inner light, corresponding to da’at . . .”