Exodus 3:1-3

1Now Moses was keeping the flock of Jethro (Reuel) his father-in-law, the priest of Midian; and he led his flock to the west side of the wilderness and came to Horeb (Sinai), the mountain of God.

2The Angel of the Lord appeared to him in a blazing flame of fire from the midst of a bush; and he looked, and behold, the bush was on fire, yet it was not consumed.

3So Moses said, “I must turn away [from the flock] and see this great sight—why the bush is not burned up.”