The essence of Shabbat, God’s rest from the work of Creation, is not just suspension of work.
There is an additional element as well: the command to rest.
Here, we must stress the fundamental distinction between rest and inactivity.
The same distinction we made between exertion and work – between a random action and a deliberate effort – exists between inactivity and rest as well.
Inactivity is random inaction, complete desistance from any exertion, whereas rest entails the practice of deliberate, purposeful inaction in preparation for further action in the future.
That is to say, although rest does not involve exertion, it, too, is a creative act, because it creates the possibility and prepares for all further creation.
In addition, rest has another, more spiritual aspect.
In the course of continuous, routine work, it is generally impossible to appreciate the totality of the work that has been done, to attain perspective and plan for the future.
Rest, on the other hand, enables one to take stock in this way, which is necessary for perceiving the spiritual significance of one’s work.
Thus, even though, with respect to exertion, rest is a state of stillness and passivity, with respect to the purposeful-essential aspect of work and creation, it is an incredibly dynamic activity.
Rabbi Adin Steinsaltz