Exodus 20:24-26

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.”