Now Moses fed the sheep of Jethro his father in law, the priest of Madian: and he drove the flock to the inner parts of the desert, and came to the mountain of God, Horeb. And the Lord appeared to him in a flame of fire out of the midst of a bush: and he saw that the bush was on fire and was not burnt. And Moses said: I will go and see this great sight, why the bush is not burnt. And when the Lord saw that he went forward to see, he called to him out of the midst of the bush, and said: Moses, Moses. And he answered: Here I am. And he said: Come not nigh hither, put off the shoes from thy feet: for the place whereon thou standest is holy ground. And he said: I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob. Moses hid his face: for he durst not look at God.
Exodus 3:1-6