Exodus 3:2-5

Then the angel of the LORD appeared to him in a flame of fire within a bush. As Moses looked, he saw that the bush was on fire but was not consumed. So Moses thought, “I must go over and look at this remarkable sight. Why isn’t the bush burning up?” When the LORD saw that he had gone over to look, God called out to him from the bush, “Moses, Moses!” “Here I am,” he answered. “Do not come closer,” he said. “Remove the sandals from your feet, for the place where you are standing is holy ground.”