Deuteronomy 4:11-15

11You approached and stood at the foot of the mountain, a mountain ablaze to the sky above it and yet dark with a thick cloud.

12Then the Lord spoke to you from the middle of the fire; you heard speech but you could not see anything – only a voice was heard.

13And he revealed to you the covenant he has commanded you to keep, the ten commandments, writing them on two stone tablets.

14Moreover, at that same time the Lord commanded me to teach you statutes and ordinances for you to keep in the land which you are about to enter and possess.

15Be very careful, then, because you saw no form at the time the Lord spoke to you at Horeb from the middle of the fire.