Exodus 3:2-5

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. 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.’ ‘Do not come any closer,’ God said. ‘Take off your sandals, for the place where you are standing is holy ground.’