During the giving of the Law at Mount Sinai (Exodus 20:18-19, RSV), the Israelites witnessed thunder, lightning, the sound of the trumpet, and smoke covering the mountain. They asked Moses to speak to them instead of God, lest they die. 

Biblical Reference (Exodus 20:18-19, RSV):

"Now when all the people perceived the thunder and the lightning and the sound of the trumpet and the mountain smoking, the people were afraid and trembled; and they stood afar off, and said to Moses, ‘You speak to us, and we will hear; but let not God speak to us, lest we die.’”