Deuteronomy 27:7

⁵  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.

⁶  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:

⁷  And thou shalt offer peace offerings, and shalt eat there, and rejoice before the LORD thy God.

⁸  And thou shalt write upon the stones all the words of this law very plainly.

⁹  And Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the LORD thy God.