Exodus 3:1-3

1Now Moses was shepherding the flock of his father-in-law Jethro, the priest of Midian, and he led the flock to the far side of the desert and came to the mountain of God, to Horeb.

2The angel of the Lord appeared to him in a flame of fire from within a bush. He looked – and the bush was ablaze with fire, but it was not being consumed!

3So Moses thought, “I will turn aside to see this amazing sight. Why does the bush not burn up?”