According to the Midrash, the thorn bush is symbolic of the human being. It is not always the rich and famous to whom God reveals Himself. He finds people who look little and insignificant.
When the Divine Presence rests upon them, they do not even recognise that something special has happened to them. Like the thorn bush, they are aflame with spirituality. But also like the bush, they do not burn up and disintegrate.
They are overtaken with spiritual quality, but they remain normal human beings, and they add to the store of Godliness in the earthly world.