A good example of faith - Abraham.
In Genesis 22, God told Abraham to go and sacrifice his son, Isaac. (a very dramatic turn of events!)
However, this is what most people might not think about. I think ole Abraham probably smiled a little on the inside.
You see, God had already promised Abraham, even before Isaac was born, that through Isaac, and Isaac's seed, the world would be blessed. (Genesis 17)
Abraham was absolutely positive that God would keep that promise. So Abraham knew that even if he killed Isaac, somehow God would bring him back to life, in order to keep that promise. (Heb 11)
Abraham had faith in that promise.
So, when someone says a person is placing their "faith" in keeping the Sabbath, it is just a wrong use of the word "faith".