Question: What does it mean, "remember the Sabbath to keep it holy"?
Response: A more literal translation of the Hebrew for Ex.20:8 would be: "Remember the day of the Sabbath in order to sanctify it." Along with the next commandment (the 5th) to honor parents, this is the only other positive command among the ten (do as opposed to don't do something). Keeping the day in mind, not forgetting about it, so that it will be properly kept in a holy, proper, sanctified fashion is the idea here. This, of course, is the only commandment not repeated in the New Testament, and for a reason. As the book of Hebrews makes clear (cf. especially chapter four), that is because we believers in Jesus Christ are on permanent Sabbath, commanded to remember Him at all times, not just on one day, and so to sanctify Him, the Lord of the Sabbath, always in our hearts. We belong to a whole new order of things: we have a New Covenant, a new High Priest, Jesus Christ (Heb.7), and we are members of a new priesthood (Rev.1:6). The old things have passed away, and our Lord has made all things new (Rev.21:4-5).
There is more to found at the following links:
Should Christians honor Sunday as the new Sabbath?
Remember the Sabbath to keep it holy.
True Orthodoxy and False Creeds
Remember the Sabbath (in SR #5)
The Millennial Sabbath (in SR #5)
The 10 Commandments (in part 5 of "The Satanic Rebellion")
The 10 Commandments (in "Hamartiology", part 3B of "Bible Basics")
The Dangers of Messianic Legalism.
The Dangers of Messianic Legalism II
The Dangers of Messianic Legalism III
Yours in Christ,