Deuteronomy 27:4-6

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