Altogether three reasons were given to Israel for remembering the Sabbath. The first, given here, is rooted in creation.
For in six days the LORD made heaven and earth, the sea, and all that is in them, and rested on the seventh day. Therefore the LORD blessed the Sabbath day and made it holy (Exodus 20:11 ESV).
When Moses calls the next generation to covenant renewal and restates this command, much remains the same, but the grounds are significantly different.
You shall remember that you were a slave in the land of Egypt, and the LORD your God brought you out from there with a mighty hand and an outstretched arm. Therefore the LORD your God commanded you to keep the Sabbath day (Deuteronomy 5:15 ESV).
Ultimately, I believe, that these two reasons have one unifying reason, and a hint as to how this can be is found in a yet third basis given for Sabbath remembrance.
You are to speak to the people of Israel and say, ‘Above all you shall keep my Sabbaths, for this is a sign between me and you throughout your generations, that you may know that I, the LORD, sanctify you (Exodus 31:13 ESV).’
Like circumcision and the Passover, the Sabbath is a perpetual sign throughout their generations, of His covenant. Jesus comes as the fulfillment of the law. Because of Him circumcision gives way to baptism (Colossians 2:11–13), the Passover blooms into the Lord’s Supper (Luke 22:14–18ff), and the Sabbath, well, what becomes of the Sabbath? We’re clearly commanded to baptize and to remember the Supper, but no command is given concerning the Sabbath, nor the Lord’s day. Rather, we’re told:
One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. The one who observes the day, observes it in honor of the Lord (Romans 14:5–6 ESV).
Therefore let no one pass judgment on you in questions of food and drink, or with regard to a festival or a new moon or a Sabbath. These are a shadow of the things to come, but the substance belongs to Christ (Colossians 2:16–17 ESV).
What happens to the Sabbath? Jesus declares Himself Lord of the Sabbath in Matthew 12. Just prior to this Matthew records these words, “Come to me, all who labor and are heavy laden, and I will give you rest. Take my yoke upon you, and learn from me, for I am gentle and lowly in heart, and you will find rest for your souls. For my yoke is easy, and my burden is light (Matthew 11:28–30 ESV).” Hebrews 4 speaks of entering God’s rest by faith, the rest of God that He had once He had finished from His works.
Because of Jesus, our work is finished, competed perfectly for us, and now we rest. What happens to the Sabbath? We haven’t abandoned it. We’ve entered more fully into it—in Jesus. Because of His redemption, a new day has dawned, a resurrection day, a day of new creation, a day of rest.
In short the physical rest of the Old Testament Sabbath has become the salvation rest of the true Sabbath. Believers In Christ can now live in God’s Sabbath that has already dawned. Jesus’ working to accomplish this superseded the Old Testament Sabbath (John 5:17) and so does the doing of God’s work that He now requires of people—believing in the one God has sent (John 6:28, 29). In fact the Sabbath keeping now demanded is the cessation from reliance on one’s own works (Heb. 4:9, 10). —A.T. Lincoln