Deuteronomy 4:11-15

11You approached and stood at the foot of the mountain, and the mountain burned with fire to the [very] heart of the heavens: darkness, cloud and thick gloom.

12Then the Lord spoke to you from the midst of the fire; you heard the sound of the words, but you saw no form—there was only a voice.

13So He declared to you His covenant which He commanded you to follow, the Ten Commandments; and He wrote them on two tablets of stone.

14The Lord commanded me at that time to teach you the statutes and judgments, so that you might do them in the land which you are going over to possess.

15“So pay attention and watch yourselves carefully—for you did not see any form [of God] on the day the Lord spoke to you at Horeb from the midst of the fire—