Exodus 20:15-20:23
All the people witnessed the thunder and lightning, the blare of the horn and the mountain smoking; and when the people saw it, they fell back and stood at a distance. "You speak to us," they said to Moses, "and we will obey; but let not God speak to us, lest we die." Moses answered the people, "Be not afraid; for God has come only in order to test you, and in order that the fear of Him may be ever with you, so that you do not go astray." So the people remained at a distance, while Moses approached the thick cloud where God was.
The Lord said to Moses:
Thus shall you say to the Israelites: You yourselves saw that I spoke to you from the very heavens: With Me, therefore, you shall not make any gods of silver, nor shall you make for yourselves any gods of gold. Make for Me an altar of earth and sacrifice on it your burnt offerings and your sacrifices of well-being, your sheep and your oxen; in every place where I cause My name to be mentioned I will come to you and bless you. And if you make for Me an altar of stones, do not build it of hewn stones; for by wielding your tool upon them you have profaned them. Do not ascend My altar by steps, that your nakedness may not be exposed upon it.