Мидраш к Тегилим 106:5

And Moshe was a shepherd and a gentleman in a fire out of the bush. Rashbi tells what God Almighty discovered from my name and would talk to Moshe out of the bush, what this bush is tougher than any tree in the world and every bird that enters it does not go right out of it but cuts limb organs, so that Egyptian labor is difficult before the place of every slave in the world. A slave or slave Ben Horin never left Egypt but only Hagar said (Genesis 2: 2) and Pharaoh would go on him and send him and his wife and all that he had: Merom and he would talk to Moshe out of the bush as long as Israel was in such trouble