Why Do Christians Worship on Sunday Instead of Saturday? Old Covenant, New Covenant, and the Sabbath

This post is Part 1 of a two-part Sunday school series on why Christians worship on Sunday instead of Saturday. In this first article, we will lay the covenantal foundation by looking at the Old Covenant, the New Covenant, and the Sabbath. Table of contentsThe Sabbath belonged to the Old Covenant given to Israel through MosesJesus instituted the New Covenant in His bloodEach covenant had its own lawGalatians teaches freedom from the Mosaic Law, not freedom from obedienceHebrews 7:12 explains why covenantal change affects the lawWhy this prepares us for Sunday worshipConclusion The Sabbath belonged to the Old Covenant given to Israel through Moses The first thing to establish is that the Sabbath was a sign of the Mosaic Covenant given specifically to Israel. Exodus 31:13 says, “You shall keep my Sabbaths, for this is a sign between me and you throughout your generations.” Then Exodus 31:17 says, “It is a sign forever between me and the people of Israel.” That is very important. The Sabbath was not presented as a covenant sign between God and the church. It was a sign between God and Israel under the Old Covenant, which was mediated by Moses. So if someone asks, “What covenant is the seventh-day Sabbath associated with?” the answer is clear: the Old Covenant, mediated by Moses, given to Israel. That point matters because it keeps us from treating the Sabbath as though it were detached from the covenantal framework in which God gave it. The Sabbath was not a free-floating universal covenant sign for all peoples in all covenant administrations. It belonged to a specific covenant God made with Israel through Moses. Jesus instituted the New Covenant in His blood Exodus 24 contains the institution of the Old Covenant. The people agreed to the covenant’s terms, promising to obey all that the Lord had spoken. But the covenant was not formally inaugurated until blood was shed. Exodus 24:6-8 repeatedly emphasizes blood, culminating in Moses saying, “Behold the blood of the covenant that the Lord has made with you in accordance with all these words.” As your notes rightly emphasize, there is no instituting a covenant without blood. Hebrews 9:18 confirms this: “Not even the first covenant was inaugurated without blood.” That Old Testament scene prepares us to understand Luke 22. At the Last Supper, Jesus took the cup and said, “This cup that is poured out for you is the new covenant in my blood.” The parallel is striking. Moses instituted the Old Covenant with blood. Jesus instituted the New Covenant with blood. But the New Covenant is greater because it was not inaugurated with the blood of animals. It was inaugurated with the blood of Christ Himself. This means there is a real covenantal transition: Moses mediated the Old Covenant. Jesus mediates the New Covenant. And this is foundational for understanding why Christian worship is centered on Sunday rather than Saturday. We are not dealing with a minor adjustment in religious custom. We are dealing with the transition from one covenant to another, from one mediator to another. Each covenant had its own law The New Testament also makes clear that each covenant had its own law. In 1 Corinthians 9:20, Paul said, “To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law.” In context, those under the law are Jews who had not embraced Christ. Paul’s point is that he could temporarily live as one under the Mosaic Law for evangelistic reasons, but he himself was no longer under that law. Then in the next verse, Paul speaks about Gentiles: “To those outside the law I became as one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law.” Paul was careful to explain that being outside the Mosaic Law did not mean living lawlessly. He was still under authority, but that authority was now described as the law of Christ. So there is a clear distinction between the two laws and the two covenantal administrations: The Mosaic Law is associated with the Old Covenant and its mediator, Moses. The law of Christ is associated with the New Covenant and its Mediator, Jesus. That distinction matters greatly for the subject of worship. Christians are not lawless, but neither are we under the Mosaic Covenant. We belong to Christ and live under His covenant. Galatians teaches freedom from the Mosaic Law, not freedom from obedience As your notes so well say, Galatians is like our Declaration of Independence from the Mosaic Law. If there is one New Testament book that makes plain that believers are not under the Mosaic system as a covenant, it is Galatians. But even there, Paul still says in Galatians 6:2, “Bear one another’s burdens, and so fulfill the law of Christ.” That is important. Freedom from the Mosaic Law does not mean freedom from obedience. It means freedom from the old covenantal administration and from any attempt to be justified by law-keeping. Christians are still called to holiness, love, and obedience, but our obedience is now tied to Christ and the New Covenant He mediates. Hebrews 7:12 explains why covenantal change affects the law Now we come to the verse that helps explain why this transition could take place at all. Hebrews 7:12 says, “For when there is a change in the priesthood, there is necessarily a change in the law as well.” This verse gives the theological explanation for the transition. Jesus did not come merely to continue the Mosaic system. He came to fulfill it and establish a better covenant with a better priesthood. Under the Old Covenant, the priesthood was Levitical. Under the New Covenant, Jesus is our great High Priest. Since the priesthood changed, the law-covenant order connected to that priesthood also changed. That means we should expect changes in how God’s people relate to covenant signs and worship. The Old Covenant was associated with the seventh day. The New Covenant is associated with Christ’s resurrection on the first day of the week. Hebrews 7:12 does not merely tell us that something changed. It tells us why change was necessary. Once the priesthood changed from Levi to Christ, the covenantal order tied to that priesthood could not remain exactly the same. Why this prepares us for Sunday worship At this point, we are in a much better position to answer the question, Why do Christians worship on Sunday instead of Saturday? Part 1 does not yet trace every New Testament first-day text, but it lays the necessary theological foundation. The seventh-day Sabbath belonged to the Old Covenant given to Israel through Moses. Jesus instituted the New Covenant in His blood. Paul distinguished between the Mosaic Law and the law of Christ. Hebrews 7:12 explains that when the priesthood changed, the law-covenant order changed as well. So the move from Saturday to Sunday is not arbitrary. It is tied to the movement from Moses to Christ, from the old covenantal order to the new, and from shadow to fulfillment. In Part 2, we can look more directly at how the New Testament connects the first day of the week with Christ’s resurrection and the worship of God’s people. Conclusion Why do Christians worship on Sunday instead of Saturday? Because Christ brought a covenantal transition that changed how God’s people relate to the law, the priesthood, and covenant signs. The Sabbath was a sign of the Old Covenant between God and Israel. Jesus came as the Mediator of the New Covenant and instituted it in His own blood. And Hebrews 7:12 explains that when the priesthood changed, the law changed as well. This is why the discussion is much bigger than personal preference or church tradition. It is about understanding redemptive history rightly. It is about seeing that the Old Covenant was associated with the seventh day, while the New Covenant is associated with Christ’s resurrection and the first day of the week. That is the foundation, and in Part 2, we can build on it further: we will look more directly at Christ’s resurrection on the first day of the week, the early church’s pattern of gathering, and why Sunday is rightly called the Lord’s Day.