One reason I feel a need for rest, I think, has to do with the natural rhythms of life. Like the seasons that rhythmically cycle through each year, there are rhythms of rest and work that seem to cycle through the year as well. The rhythm of summer feels like it lends itself more to a time of rest, a time to be filled up, refueled by things that only the summer can offer. This is especially true for the traditional teacher that has summers "off". Fresh greens and fruit from the gardens and orchards, after-dinner walks in the cool setting sun, trips to the swimming hole, fish fries; these are all things that seem like they could bring rest. So, one reason I feel that need for rest at this time might be because it is naturally a time to rest.
The creation story in Genesis gives me some insight into this natural cycle of rest. Genesis 2:2-3 says, "And on the seventh day God finished his work that he had done, and he rested on the seventh day from all his work that he had done. So God blessed the seventh day and made it holy, because on it God rested from all his work that he had done in creation."
First, I automatically have a question when I read this. Why did God rest on the 7th day? My initial reaction to that question would be to say that he rested because he was tired (which betrays my own assumptions about the nature of rest). But that would be importing something into the text that isn't there. Nowhere does it say God rested because he was tired or because He needed it. God rested because his work was done. We see further in Exodus 31:15 that it was a rest that did bring refreshment. So, it seems like a clear pattern is set for us. God anticipates our need for rest and refreshment, because, unlike God, we are in need of these things, so he builds into the cosmos this natural pattern. It is a rest that is entered into when the work is done, not necessarily when you are tired of working, but rather when you have come to a place of completion in your work (I think this completion is something we anticipate; we get tastes of it but don't fully enter into it this side of glory).
God rested from his work of creation, but God did not cease to work altogether. Obviously, if he had, the creation would have fallen apart. Paul reminds us that in God we live and move and have our being (Acts 17:28). God created the world and sustains its existence moment by moment. If he withdraws his sustaining hand, the world would return to what it was before God initially spoke (Job 34:14-15). So, rest is not inactivity. Times of rest don't automatically mean you don't have to, or can't, do anything (Jesus rebukes the Jews that were persecuting him for healing on the Sabbath and responds by telling them that he and his Father have been working everyday since the beginning to now, John 15:17).
In a recent conversation with a friend on this topic, he told me he likes to think of times of rest as maintenance. You have done the work and now you must maintain what has been accomplished. A similar picture of this is given to us in the command to the Israelites to conquer and conquest the land of Canaan. They must first do the work of conquering the land before they can enter into the rest promised in the land (Deu. 12:9-10). However, rest in the land is not inactivity. It is actually a state of rest that can be enjoyed while at the work of conquest. It is a state of rest that is achieved when something is completed and a state of rest that is enjoyed while at work.
At this point I might know more about what rest is not rather than what rest is. Though, I might be able to at least say that rest is not the absence of work, rather it is a state of being. It is even a state one can be in while at work. Rest is part of the natural cycle of the cosmos. As creations made in the image of God we reflect a natural cycle of work and rest.
Several questions still remain...