Hebrews 4:4-10 (ESV)
For he has somewhere spoken of the seventh day in this way: "And God rested on the seventh day from all his works."  And again in this passage he said,
"They shall not enter my rest."
 Since therefore it remains for some to enter it, and those who formerly received the good news failed to enter because of disobedience,  again he appoints a certain day, "Today," saying through David so long afterward, in the words already quoted,
"Today, if you hear his voice,
do not harden your hearts."
 For if Joshua had given them rest, God would not have spoken of another day later on.  So then, there remains a Sabbath rest for the people of God,  for whoever has entered God's rest has also rested from his works as God did from his.
Today is the Sabbath, for today we have entered his rest. When we hear God’s voice, that is the Gospel, and hear that our sins are forgiven, believing this we enter into his rest, which is the Sabbath. Christian’s no longer observe the Sabbath with rules etc. Christ is our Sabbath rest, we rest in him. And it is true rest, rest from the law. It isn’t a work to rest for the Christian. People who try to live by the O.T. Rules for Sabbath rest, don’t rest at all. It is work to put up with all those rules, constantly looking over the rules to see if you can do this or that. And moving it to Sunday but following the same rules is nothing more than the dog returning to his vomit. Want your kids to resent Christianity? Give them the Sabbath rules on Sunday. Tell them they can’t, can’t, can’t. I mean what kid really wants to be cooped up in the house all day. Is that really rest? Since when is play not rest? But Jesus is our Sabbath rest. We no longer need to be concerned about such silly things.