The stay in the desert was temporary, transitory. There, everyone did as whatever was right in his own eyes. The Torah was given in Sinai, not to be kept in the desert but in the Promised Land. That's why it was impossible to keep many of the commandments in the desert and they had to improvise and do what they could in that transitory situation.

Moshe Rabbenu was preparing the people to step ahead from the forty transitory and preparatory years to a new, totally different situation. This text says that when they were in the desert they had not yet come to the rest and the inheritance. The rest is one thing and the inheritance another. The rest has to do with a state of mind and the inheritance with something physical, the land. Each tribe was to receive a piece of land as inheritance and each family would receive their place for living where they could feel at home and have their souls rest.

Now, since the Torah was written in the first place for the Land of Israel, all the commandments are related to the life of the twelve tribes in it. Without their presence in the Land it's impossible to fulfill the whole Torah, and it's also impossible to achieve complete rest. It's interesting to see the relationship between emotional rest and the fulfillment of the commandments. The lack of commandments creates mental instability which is contrary to rest. They couldn't keep many of the commandments in the desert that's why they didn't rest in their souls. But in the Land they would be able to keep the commandments and thus reach rest.

Shavua tov,