Genesis 2:3

So God blessed the seventh day and sanctified it (as His own, that is, set it apart as holy from other days), because in it He rested from all His work which He had created and done. 

God rested after all His work.  The seventh day was set apart as a holy day from the other days and a sign of the covenant.  It is good for man to rest just like God from all our work. The world would prefer to make it just another day without a God to reflect upon or a day to rest.  We as believers need this day to reset, reflect and refuel and set ourselves apart.