An angel of G-d appeared to him in the heart of a blazing fire from the midst of a thorn bush. As Moses gazed, he saw the bush was on fire, but the bush was not being consumed.
Shemot 3:2
Allegorically, the lowly thorn bush signifies simple, sincere folk, while learned, accomplished people are like the prodigious fruit tree. Although the simple folk are inferior in their accomplishments; their fiery yearning for G-d is never consummated; in this sense, they are spiritually superior to those who are aware of their accomplishments but are therefore prone to complacency.
By appearing to Moses in a thorn bush, G-d indicated to him that in order to be a true leader and redeem his people, he would have to recognize the intrinsic value of the simple folk. In order to receive the Torah, which binds finite man to the infinite G-d, Moses would have to appreciate and teach others to appreciate the unrequited yearning for G-d that only simple folk demonstrate so eloquently. Because G-d is infinite, no matter how spiritually accomplished we may be, there will always be uncharted realms for us to traverse in our journey to Him. True appreciation for the infinity of G-d and His Torah is therefore reflected in our appreciation of the unquenchable thirst for G-d evinced by unlettered folk and our desire to emulate it.
Moses understood this hint and applied it immediately to himself. Not satisfied with all his prior spiritual accomplishments, he was willing to abandon all his preconceived notions of reality in order to understand the anomaly of the burning bush. He said, "let me turn away from where I am in order to approach there." In response, "when G-d saw that he had turned aside to look, He called to him from the midst of the bush."
The aspiration implicit in "Let me turn away from where I am in order to approach there" is the foundation of any relationship with G-d. It is this aspiration that makes us human, i.e., beings that aspire to transcend animal existence in search of intellectual depth and spiritual self-refinement. It enables us to access our innate and infinite potentials. In particular, it enables us to focus our intellect in solitary meditation in order to climb the ladder of Divine consciousness.
As spiritual seekers, we live in a process of unending ascent: whatever level of Divine consciousness we reach, we always aspire to ascend further. The force of this aspiration unlocks all our human potentials, strengthening our intellect, emotions, and senses. We are constantly blessed with new insight and understanding, which in turn lead us on the dialectic path toward a deeper relationship with G-d.
--From Kehot's
Chumash Shemot