Deuteronomy 27:2-4

2And it shall be on the day when ye shall pass over Jordan unto the land which Yhwh thy God giveth thee, that thou shalt set thee up great stones, and plaister them with plaister:

3And thou shalt write upon them all the words of this law, when thou art passed over, that thou mayest go in unto the land which Yhwh thy God giveth thee, a land that floweth with milk and honey; as Yhwh God of thy fathers hath promised thee.

4Therefore 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.