Exodus 20:22-26

22Then Adonai said to Moses, “Say this to Bnei-Yisrael: You yourselves have seen that I have spoken to you from heaven.

23Do not make gods of silver alongside Me, and do not make gods of gold for yourselves.

24You are to make an altar of earth for Me, and there you will sacrifice your burnt offerings, your fellowship offerings—your sheep and your cattle. In every place where I cause My name to be mentioned I will come to you and bless you.

25When you make for Me an altar of stones, do not build it from cut stone, for if you use a tool on it, you will have profaned it.

26Nor are you to go up to My altar on steps, so that your nakedness would not be uncovered while on it.”