Exodus 20:24-26

“Build for me an altar made of earth, and offer your sacrifices to me—your burnt offerings and peace offerings, your sheep and goats, and your cattle. Build my altar wherever I cause my name to be remembered, and I will come to you and bless you. If you use stones to build my altar, use only natural, uncut stones. Do not shape the stones with a tool, for that would make the altar unfit for holy use. And do not approach my altar by going up steps. If you do, someone might look up under your clothing and see your nakedness.