Exodus 20:18-20

And all the people perceived the thunderings, and the lightnings, and the voice of the trumpet, and the mountain smoking: and when the people saw it, they trembled, and stood afar off. And they said unto Moses, Speak thou with us, and we will hear; but let not God speak with us, lest we die. And Moses said unto the people, Fear not: for God is come to prove you, and that his fear may be before you, that ye sin not.