Why are Abraham, Isaac, Jacob, Moses, Aaron, Joseph and David called Shepherds?
Some were indeed shepherds, and this was, at times, the primary reason they were chosen to lead.
This is particularly true of Moses.
The Midrash tells us that just before God appeared to Moses in the burning bush, Moses was chasing a lost sheep, and God said to him: “You will lead Israel because you have mercy over a flock.” (Midrash, Exodus Rabbah 2).
In the Song of Songs, the Shepherd (God) says to the shepherdess (Israel): “My sister, my friend, my dove, my innocent one.” (Song of Songs 5:2). “My friend” should be translated as “my shepherdess, my source of nourishment.”
These examples from the Midrash confirm the saying that Israel feeds God.
A definition of food helps to make this statement less anthropomorphic.
Taking nourishment unites body and soul.
By nourishing the human body, I enabled the soul to reside there.
Assuming, as we do, that God is the soul of the universe, then behaving in such a way that God will be present in the world is metaphorical “nourishment.”
Individuals who conduct their lives in such a way that God will remain in the world, and not disengage Himself from it, can thus be called the shepherds of God, His nourishers.
The relationship is reciprocal.
The Psalms often refer to God as the Shepherd of Israel, as in “The Lord is my shepherd, I shall not want.”
There is no better way to say that God ensures us sustenance and life.
And we ensure His Presence on earth by “nourishing” Him.
This is why He calls us “my friends.”
A friend is one who nourishes.
The Sages draw on this concept to make a somewhat audacious interpretation of the verse in Isaiah, “So you are my witnesses, declares that Lord, and I am God,” (Isaiah 43:10) which they reformulate as “If you are my witnesses, I am God.” (Talmud, Hagigah.16b)
The idea is that God is saying, “As long as you are my witnesses, I am God. If not, I am no longer God.”
Without us, without our efforts, if we do not serve Him, God certainly exists, but He is not present or visible in the world.
This is the true definition of a witness.
A witness is not only someone who is present at an event.
It is also someone who can provide an account of it.
This is one of the functions of Sukkot.
In the sukkah we live in the shadow of God, in the palm of His hand, embraced by His arm, as it is said “And I sheltered you with My hand.” (Isaiah 51:16)
The Seven Shepherds we invite to the sukkah are in fact none other than ourselves.
We become the Shepherds of God; we discover our own ideal selves in the Patriarchs.
–Rabbi Adin Steinsaltz
From “The Three Pilgrim Festivals” p. 272-277, in The Seven Lights by Rabbi Adin Steinsaltz