Leviticus 23:3

For six days work may be done, but the seventh day is the Sabbath of complete rest, a holy convocation (calling together). You shall not do any work (on that day) it is the Sabbath of the Lord wherever you may be.

God invented rest and rested Himself from all His work.  The world today tries to pull us away from rest and to come together.  Many of us can remember when no shops were open on Sunday.  Rest and coming together draws our focus back to God from the busy world.