Exodus 3:2-4 NIV

2 There the angel of the LORD 1 appeared to him in flames of fire2 from within a bush.3 Moses saw that though the bush was on fire it did not burn up.

References for Exodus 3:2

3 So Moses thought, "I will go over and see this strange sight--why the bush does not burn up."
4 When the LORD saw that he had gone over to look, God called4 to him from within the bush,5 "Moses! Moses!" And Moses said, "Here I am."6

References for Exodus 3:4