Several points stand out in this passage:
1) The Sabbath is a sign of who the true God is. The true God is the Creator.
2) The Sabbath is a sign of God's people.
3) The Sabbath(s) belongs to God (verse 13). He designed the time as holy, not Moses or any other man.
4) The Sabbath sanctifies. It sets apart the man who keeps it by showing him to be distinct from the rest of the culture.
5) Sabbath-breaking incurs the death penalty.
6) The Sabbath is a perpetual covenant. The Old Covenant was not a perpetual covenant; it has been replaced by the New.
7) The Sabbath covenant is separate and distinct from the Old Covenant given at Mt. Sinai. Not only did the events in this passage take place 40 days after the proposal and acceptance of the Old Covenant, but God re-revealed the Sabbath to the children of Israel (because they were in Egypt for so long they had forgotten it) right after they left Egypt and days before they arrived at Mt. Sinai. The lesson of the manna, which demonstrated the difference in the days of the week (Exodus 16), happened before the rest of the law was given via the Old Covenant. Even though the Old Covenant - that specific agreement - has passed away, that does not mean that the eternal code of conduct on which the agreement was based has passed away. Notice that idolatry and adultery are both still sin (and nobody considers those laws to be "Jewish").
8) This was spoken to the people that God was working with at the time - Israel. Part of Jesus Christ's earthly ministry was to "fulfill" the law, and not to destroy it (Matthew 5:17-18)! The rest of Matthew 5 shows Him magnifying various points of law to reveal the true intent behind them. Jesus Christ says in Mark 2:27 that the Sabbath was made for mankind, not just for physical Israel! Galatians 6:16 shows that the designation of "Israel" under the New Covenant is now a designation of the church. And the Bible shows the New Testament church, Christ included, observing the Sabbath and not the first day of the week.
David C. Grabbe
Notice which day is "the Lord's Day." God calls the Sabbaths "My Sabbaths." The Sabbaths, weekly and annual, are His; they do not belong to us, nor are they "Jewish Sabbaths" or "Gentile Sabbaths." The Sabbath is a space of time. That time, whenever it arrives, is not ours but God's. If we appropriate it for our own use, whether for work or pleasure, we are stealing that time from God! In Exodus 20:8, He commands us to "keep it holy." God made it holy time, and commands us to keep it holy rather than profane it.
"Surely My Sabbaths you shall keep, for it is a sign between Me and you throughout your generations, that you may know that I am the Lord who sanctifies you" (Exodus 31:13). Here, then, is the purpose of the Sabbath: ". . . it is a sign." A sign is a badge, symbol, mark, or token of identity. Webster's Dictionary defines a sign as "a display used to identify or advertise a place of business or a product. Something indicating the presence or existence of something else."
The word Moses wrote in Hebrew is 'owth, which means "a sign, signal, distinguishing mark, banner, remembrance, warning; a token, ensign, standard, miracle, proof" (Brown, Driver & Briggs Hebrew Lexicon). A banner or flag identifies a nation or group. A signal like a beacon announces the existence of something, like a rocky shore, that others need to be warned about. A token is a visible sign that serves to make something known, such as a white flag is a token of surrender.
God commands His people to keep His Sabbaths as a sign. It is a sign between God's people and God: "It is a sign between Me and you." It is a badge or token of identity, advertising, announcing, or proclaiming certain identifying knowledge: ". . . that you may know that I am the Lord who sanctifies you."
The Sabbath is the sign that identifies to people who their God is. It is the sign by which we may know that He is the Lord. It identifies God, and by so doing, it identifies who His people are as well.
A sign identifies a business, a street, a product, etc., and so does the Sabbath! It identifies God's people. Notice also that this covenant, made after the ratification of the Old Covenant, bound the Sabbath as a "perpetual covenant" upon God's people.
Richard T. Ritenbaugh
It was Christ, as the God of the Old Testament, who actually created the Sabbath (John 1:1-3). It is a sign that identifies God's people just as a sign identifies a business or a street. Notice also that this covenant, made after the ratification of the Old Covenant, bound the Sabbath as a "perpetual covenant" upon God's people. Since the Sabbath has been in force from Creation, it is not just for the Jews, but for the foreigner and all mankind as well. All who keep the Sabbath properly are blessed.
Martin G. Collins
The Fourth Commandment
Other Forerunner Commentary entries containing Exodus 31:12: