Deuteronomy 4:11-13

And you came near and stood at the foot of the mountain, while the mountain burned with fire to the heart of heaven, wrapped in darkness, cloud, and gloom. Then the LORD spoke to you out of the midst of the fire. You heard the sound of words, but saw no form; there was only a voice. And he declared to you his covenant, which he commanded you to perform, that is, the Ten Commandments, and he wrote them on two tablets of stone.