Deuteronomy 27:2-6

2When you cross the Jordan River to the land the Lord your God is giving you, you must erect great stones and cover them with plaster.

3Then you must inscribe on them all the words of this law when you cross over, so that you may enter the land the Lord your God is giving you, a land flowing with milk and honey just as the Lord, the God of your ancestors, said to you.

4So when you cross the Jordan you must erect on Mount Ebal these stones about which I am commanding you today, and you must cover them with plaster.

5Then you must build an altar there to the Lord your God, an altar of stones – do not use an iron tool on them.

6You must build the altar of the Lord your God with whole stones and offer burnt offerings on it to the Lord your God.