Exodus 31:12-17 teach us that the Sabbath is a sign of God’s covenant with Israel established at Mt. Sinai. The passage is arranged chiastically:
A Verse 13: the Sabbath is a sign between the Lord and the children of Israel.
B Verse 14a: you shall keep the Sabbath.
C Verse 14b: Whoever profanes the Sabbath shall be put to death.
D Verse 15a: Work shall be done for six days, but the seventh is the sabbath of rest.
C’ Verse 15b: Whoever does any work on it shall be put to death.
B’ Verse 16: The children of Israel shall keep the Sabbath as a perpetual covenant.
A’ Verse 17: It is a sign between me and the children of Israel forever.
At the center is the requirement of the Sabbath – no work, in 14b and 15b the penalty for failing to observe it, in 14a and 16 the requirement to keep, and in 13 and 17 the establishment of the Sabbath as a sign.
There were many signs in the Mosaic covenant. The tabernacle and all its furnishings, the priesthood, the altars, the sacrifices, and the ritual cleansings are only the most prominent of them. But in this passage the Lord calls special attention to the Sabbath and says, it is a sign. He does not say that of any other ceremony associated with the temple.
Furthermore, it is a sign that their God is the Lord who sanctifies them. As the rainbow reminds us of God’s promise never again to destroy the earth with a flood and circumcision that God will be the God of Abraham and his children, so the Sabbath reminds us that God sanctifies us.
But we must ask, why? Why is the Sabbath the particular sign of the Mosaic covenant? The answer lies in the law and the tabernacle. The tabernacle was God’s dwelling place among his people, the fulfillment of the promise to Abraham that he would be his God and the God of his children. The Holy One had come to dwell among them. The law did two things. It showed the people their sin (Romans 5:13-14) and the way of approach to God through the sacrifices and cleansings. They were unholy and could not have a place in God’s while they remained unclean with their sins. Therefore, the way into God’s house was a bloody one. Sin must be atoned. The Sabbath was a gracious declaration by God that he would sanctify them and bring them into his house and his place of rest (Ps. 132:14).
That is one other reason why we should still observe the Sabbath Day today. It is a weekly reminder that coming into the most holy place, God’s presence, to have fellowship with him and to worship him is possible only because he cleanses us from our sins.