Moses brought our people together in the desert, and the angel spoke to him on Mount Sinai. There he was given these life-giving words to pass on to us.
What is the use of the Law? It was given later to show that we sin. But it was only supposed to last until the coming of that descendant who was given the promise. In fact, angels gave the Law to Moses, and he gave it to the people.
You were asking for a prophet the day you were gathered at Mount Sinai and said to the LORD, "Please don't let us hear your voice or see this terrible fire again--if we do, we will die!"