It is significant that God's Ten Commandments are found twice in the Bible (Exodus 20:3-17 and Deuteronomy 5:6-21). In fact, "Deuteronomy" means "the Second Law." The two are worded identically, with a few exceptions.
The most significant of these changes is in connection with the reason given for obeying the fourth commandment, to "keep the sabbath day." In Exodus, the reason given is: "For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day" (Exodus 20:11). Here in "the second law," the reason given is that God saved Israel out of bondage in Egypt, and now was about to enter the Promised Land. In other words, when the Israelites observed each Sabbath day in rest and worship, they were acknowledging God as both their Creator and their Redeemer.
Christians also, as they devote every seventh day as a day of rest and worship, should be remembering God for His finished creation ("the heavens and the earth were finished"--Genesis 2:1) and His finished redemption ("It is finished" was Christ's victory cry on the cross--John 19:30).
The word "Sabbath" means "rest," of course--not "Saturday" or "Sunday" or even "seventh" (the word for "seventh" in Hebrew is similar, but distinctly different from that for "sabbath"). Most Christians now believe it is appropriate to honor the Lord Jesus (who is both their Creator and Redeemer) to take their seventh day of rest and worship on the first day of each week, thereby recognizing both His finished work of redemption and also His finished work of creation. HMM http://www.icr.org/article/5989/