“Now when forty years had passed, an angel appeared to him in the wilderness of Mount Sinai, in a flame of fire in a bush. When Moses saw it, he was amazed at the sight, and as he drew near to look, there came the voice of the Lord: ‘I am the God of your fathers, the God of Abraham and of Isaac and of Jacob.’ And Moses trembled and did not dare to look. Then the Lord said to him, ‘Take off the sandals from your feet, for the place where you are standing is holy ground. I have surely seen the affliction of my people who are in Egypt, and have heard their groaning, and I have come down to deliver them. And now come, I will send you to Egypt.’ (ESV)