Now Moses was tending the flock of Jethro his father-in-law, the priest of Midian, and he led the flock to the far side of the wilderness and came to Horeb, the mountain of God.
References for Exodus 3:1
There the angel of the LORD appeared to him in flames of fire from within a bush. Moses saw that though the bush was on fire it did not burn up.
References for Exodus 3:2
So Moses thought, “I will go over and see this strange sight—why the bush does not burn up.”
When the LORD saw that he had gone over to look, God called to him from within the bush, “Moses! Moses!” And Moses said, “Here I am.”
References for Exodus 3:4