Here are the notes from Thinking Matters Hamilton’s latest worldview study. The path to the conclusion was pretty complex and intense, but I think where we ended was clear and well-supported:
There is ample biblical evidence that the Sabbath is strictly a sign of the Mosaic covenant. There is no biblical evidence that it should be observed by Christians, and a fair amount pointing the other way. It has been fulfilled in Jesus (see Matthew 11:28), and so we now live in an eternal, spiritual Sabbath, which the repeating, physical Sabbath pointed to. Thus, observing any kind of Sabbath day is purely a matter of conscience—we are free to do it or not, as our own convictions require.