Deuteronomy 27:4-8

Therefore it shall be when ye be gone over Jordan, that ye shall set up these stones, which I command you this day, in mount Ebal, and thou shalt plaister them with plaister.

And there shalt thou build an altar unto the LORD thy God, an altar of stones: thou shalt not lift up any iron tool upon them.

Thou shalt build the altar of the LORD thy God of whole stones: and thou shalt offer burnt offerings thereon unto the LORD thy God:

And thou shalt offer peace offerings, and shalt eat there, and rejoice before the LORD thy God.

And thou shalt write upon the stones all the words of this law very plainly.