Deuteronomy 27:4-7

4And when you have crossed over the Jordan, you shall set up these stones, concerning which I command you today, on Mount Ebal, and you shall plaster them with plaster.

5And there you shall build an altar to the Lord your God, an altar of stones. You shall wield no iron tool on them;

6you shall build an altar to the Lord your God of uncut stones. And you shall offer burnt offerings on it to the Lord your God,

7and you shall sacrifice peace offerings and shall eat there, and you shall rejoice before the Lord your God.