The LORD said to Moses: "Say this to the Israelites: You saw for yourselves how I spoke with you from heaven.
References for Exodus 20:22
Don't make alongside me gods of silver or gold for yourselves.
Make for me an altar from fertile soil on which to sacrifice your entirely burned offerings, your well-being sacrifices, your sheep, and your oxen. I will come to you and bless you in every place where I make sure my name is remembered.
But if you do make for me an altar from stones, don't build it with chiseled stone since using your chisel on the stone will make it impure.
Don't climb onto my altar using steps: then your genitals won't be exposed by doing so."