Deuteronomy 4:11-13

And ye came near and stood under the mountain; and the mountain burned with fire unto the midst of heaven, with darkness, clouds, and thick darkness. And the LORD spake unto you out of the midst of the fire: ye heard the voice of the words, but saw no similitude; only ye heard a voice. And he declared unto you his covenant, which he commanded you to perform, even ten commandments; and he wrote them upon two tables of stone.