Read Ellen G. White, pages 968-970, in The SDA Bible Commentary, vol. 7; “The Observance of the Sabbath,” pages 349-351, in Testimonies for the Church, vol. 6; “From the Red Sea to Sinai,” pages 295-297, in Patriarchs and Prophets.
The Ten Commandments define comprehensively and fundamentally the divine-human and human-human relationships.
The commandment at the center of the Decalogue is the Sabbath commandment. It identifies the Lord of the Sabbath in a special way and indicates His sphere of authority and ownership. Note these two aspects: 1. the identity of the Deity: Yahweh (LORD), who is the Creator (Exodus 20:11, Exodus 31:17), and who thus holds a unique place; 2. the sphere of His ownership and authority — “the heavens and the earth, the sea and all that is in them” (Exodus 20:11; compare Exodus 31:17). In these two aspects, the Sabbath commandment has the characteristics that are typical of seals of international, ancient Near-Eastern treaty documents. These seals are typically in the center of the treaty documents and also contain 1. the identity of deity (usually a pagan god) and 2. the sphere of ownership and authority (usually a limited geographical area).
“The sanctification of the Spirit signalizes the difference between those who have the seal of God and those who keep a spurious rest day.
When the test comes, it will be clearly shown what the mark of the beast is. It is the keeping of Sunday …
Thus the distinction is drawn between the loyal and the disloyal. Those who desire to have the seal of God in their foreheads must keep the Sabbath of the fourth commandment.” — Ellen G. White, The SDA Bible Commentary, vol. 7, pages 980, 981.
The Sabbath is a covenant sign that reaches forward to the time when the plan of salvation will be consummated. It points back to Creation and, as a sign of the covenant of grace, it points us to the final re-creation, when God makes all things new.