Exodus 20:22-26 - Instructions For Building Altars
22 And Yahweh said to Moses, "Thus you will say to the {Israelites}, 'You yourselves have seen that I have spoken to you from the heavens. 23 You will not make alongside me gods of silver, and gods of gold you will not make for yourselves.
24 An altar of earth you will make for me, and you will sacrifice on it your burnt offerings and your fellowship offerings, your sheep and your cattle. In every place where I cause my name to be remembered, I will come to you, and I will bless you. 25 And if you make an altar of stones for me, you will not build them [as] hewn stone, because if you use your chisel on it, you have defiled it. 26 You will not go up with steps onto my altar, that your nakedness not be exposed on it.'