I think that the portion where he muses about the Sabbath is much of the heart of this section, though I doubt that's what he intended.  I wish that it *had* been his intention, because I would have loved to see him keep going with it.

Sabbath has come to mean the day we go to church.  But this isn't how God set it up.  Exodus 16 and Exodus 20 both talk about the Sabbath, and Exodus 20 is where it really gets set out in decent order.  And nowhere does it say anything about going to church.  It's a day of rest.  It's a day to remember that even God himself rested from the work of creation.  It has nothing to do with going to church, but it has everything to do with remember that we are God's children.

This is a huge topic and issue, the Sabbath.  God's rebuttal to the Egyptian emphasis on production and enslavement for the sake of production.  He had just brought his people out of that environment, and wanted to try and set the stage for them to have a different view of the world and their place in it.  Their value did not lie in what they produced.  Their value rested in their identity as children of God.  This is where our identity lies, but our culture has insisted on returning back to the Egyptian enslavement model - wage-slaves if not truly slaves.  It's not who we are, it's what we wear.  What we drive.  Where we live.  Whether we have an office or a cube.  How nice our cell phone is.  If you need to work 7 days a week in order to have all the right stuff, then buckle down and do it. 

If this isn't slavery, I'm not sure what else to call it. 

The Sabbath flies in the face of all that, and says to rest and not worry about what you do or produce or consume.  Focus on who you are, and therefore on the God that made you and saved you.  This is where your value stems from.  We have so much to learn as the church about the Sabbath, about the importance of being instead of doing.