Israel needed to know the significance of both their unusual escape from Egypt, and their unusual entrance into the Land of Canaan, and that the Lord was responsible for both. Therefore, He wanted them to keep a special law that He delivered to them, which we commonly call, The Law of Moses. Watch what the Lord wanted them to do before they went too far into the land,

Now Moses, with the elders of Israel, commanded the people, saying: “Keep all the commandments which I command you today. And it shall be, on the day when you cross over the Jordan to the land which the Lord your God is giving you, that you shall set up for yourselves large stones, and whitewash them with lime. You shall write on them all the words of this law, when you have crossed over, that you may enter the land which the Lord your God is giving you, ‘a land flowing with milk and honey,’ just as the Lord God of your fathers promised you” (Deuteronomy 27.1–3).

As they entered the Land of Canaan, the Lord wanted Israel to know that their entrance into the land, and their continued stay in it, depended upon their keeping of the Law that He delivered to them. Therefore, He wanted them to write on stones the entire Law as part of the entrance into the land.

Writing it on stone would remind them of the unchangeableness of the Lord’s Law.