Exodus 20:8-11 Remember the Sabbath day, to keep it holy. Six days you shall labor and do all your work, but the seventh day is the Sabbath of Yahweh your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who is within your gates. For in six days Yahweh made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore Yahweh blessed the Sabbath day and hallowed it.
Deuteronomy 5:12-15 Observe the Sabbath day, to keep it holy, as Yahweh your God commanded you. Six days you shall labor and do all your work, but the seventh day is the Sabbath of Yahweh your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your ox, nor your donkey, nor any of your cattle, nor your stranger who is within your gates, that your male servant and your female servant may rest as well as you. And remember that you were a slave in the land of Egypt, and Yahweh your God brought you out from there by a mighty hand and by an outstretched arm; therefore Yahweh your God commanded you to keep the Sabbath day.
In passing, it should be noted that this passage puts to rest (pun fully intended) any notion that the six days of creation are anything other than regular days. God was not commanding Israel to work for six million years and then rest for one million.
In its strictest sense this commandment does not apply to the New Testament Christian. Some small Christian sects, such as the Seventh Day Adventists, attempt to follow this commandment and accuse all others of apostasy. This attempt to bind the consciences of others places them in direct conflict with the writings of the New Testament (Col. 2:16). The inner Pharisee loves these things. The inner Pharisee loves to make God's law doable so that the Lamb on the Altar becomes unnecessary.
A larger group of Christians, especially among the Reformed and Presbyterian churches, teach that Sunday is the new sabbath and so we shouldn't work or engage in leisure activities on that day. They also teach that Sunday must be the day of worship. They tend to ignore the prohibitions against food preparation and a number of the other sabbath laws.
The inner Pharisee can be seen in many of the "blue laws" that still remain. It is probably a good thing for a society to close down most of its businesses on Sunday to give people an opportunity to worship but in most cases now we just have remnants of these laws. I don't think that prohibiting sales of alcohol and ATVs on Sunday does anybody any good.
From the very beginning, the church did begin to worship on Sunday in celebration of the day in which our Lord Jesus Christ rose from the dead. But we find no evidence in the New Testament or the early church that Sunday absolutely had to be the day of worship. It was a convenient day and unique day but there was no condemnation of those who worshipped on a different day. In fact, Col. 2:16 says that its wrong to judge people based upon their day of worship. Actually, the early church met daily and Sunday was the day in which the Eucharist was celebrated (sometimes more than once a week in depending upon the location). Calvin, Luther, Ursinus, the Lutheran Confessions and the Reformed Confessions all teach that Sunday is not some sort of binding day on which a person must worship. The Heidelberg Catechism explains the commandment as teaching primarily that the "ministry of the gospel and the schools be maintained." It does refer to Sunday as the sabbath but does not describe it a day of rest from earthly labors. It also teaches that every day we should yield ourselves to the Lord in order to begin the eternal sabbath.
Hebrews 4 does speak of a Sabbath rest that still remains. In the context, the author of the Epistle to the Hebrews is writing to Christians who still want to go to the temple and offer sacrifices to God even though the one true sacrifice of the Lamb on the Altar has already taken place. Hebrews 4 says that is through faith in the Lamb on the Altar that we will enter into the eternal Sabbath-rest when the Lamb returns. The Epistle to the Hebrews makes it abundantly clear that we will not enter that Sabbath-rest by our own works. Hebrews 10 does tell us not to forsake the assembling of ourselves together and says some pretty harsh things about those who do but it does not teach what the Westminster Confession and the Puritans teach in regards to Christian sabbatarianism.
The command to observe the sabbath day is fulfilled in principle in the worship of the Lamb on the Altar. Ultimately, if you view worship of the Lamb on the Altar as a commandment to be obeyed then you are breaking that commandment. Worship is receiving by faith what the Lamb gives. Worship of the Lamb doesn't make the Lamb any better and it doesn't earn you any points with the Lamb. Worship is for your benefit. The Lamb has rescued you from sin, death, and the power of the devil and now he gives you His Gospel in His Word and in His body and blood. Why would you even need anyone to command you to take these awesome gifts? Why wouldn't you want to carry this Word around with you every day?