Exodus 20:22-26 - Instructions For Building Altars
22 The LORD told Moses, "This is what you are to say to the Israelis, "You have seen for yourselves that I spoke to you from heaven. 23 You are not to make gods of silver alongside me, nor are you to make for yourselves gods of gold.
24 You are to make an altar of earth for me, and you are to sacrifice on it your burnt offerings and peace offerings, your sheep, and your cattle. Everywhere I cause my name to be remembered, I'll come to you and bless you. 25 If you make an altar of stone for me, you must not build it of cut stones, because if you strike it with your chisel, you will profane it. 26 You are not to ascend to my altar on steps, so that your nakedness may not be exposed on it.'"