Deuteronomy 4:11-12

4:11 You approached and stood at the foot of the mountain, a mountain ablaze to the sky above it and yet dark with a thick cloud. 4:12 Then 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.

Deuteronomy 4:33

4:33 Have a people ever heard the voice of God speaking from the middle of fire, as you yourselves have, and lived to tell about it?