I've been asked a couple of times about the Sabbath and Lord's Day recently. Why do we worship on the Lord's Day instead of the Sabbath? Why don't we observe the Sabbath religiously? What does it mean that Jesus is the Sabbath Lord? How did Jesus Fulfill the Sabbath? Why was breaking the Sabbath a capital offense in the OT? Here's how I understand all this:

The Sabbath is called "God's Rest" in scripture. There are a few other things with that name in Scripture, among them the Promised Land and Heaven (Heb 3 to 4). Old Testament Israel was built around acting out physical ceremonies in order to reflect spiritual realities (Heb 10:1, Col 2:17). In the case of the Sabbath, they were reflecting the end of God's Work on earth (Gen 2:2-3), and God's Rest in heaven which will be shared with us after the end of the world. Following the metaphor, in the OT, to reject the Sabbath physically would have been (by reflection) like rejecting heaven spiritually; a rejection of God's rest and peace. So the physical death penalty in the OT is an appropriate reflection of the spiritual death penalty which follows a rejection of God's salvation and peace with God (Ex 31:12-17).

When Israel was on its way to the promised land, they rejected God and hardened their hearts. So God said about them, "they will never enter my rest", and made them wander in the desert until that generation was gone. The psalmist later says about this, "Today, if you hear his voice, do not harden your hearts as Israel did in the wilderness". Hebrews 3:7-4:13 cites both of these passages, and makes a connection between them, saying "As long as it is called today, encourage one another so that you don't harden your hearts". Then saying, "We who have believed enter that rest" and "God set aside a certain day, calling it 'today'", and, "there remains for some to enter that rest". So believers enter into that rest, and those elect who have not yet believed will enter it later. The new day of entering into God's rest, in the New Covenant, is every day that we call "today", so basically every day. Every day is the Sabbath for Christians. We are called to strive to enter into God's rest every day, and keep every day holy.

But then why Sunday? And why do we work? Saturday is the sabbath, but Christians worship on Sunday. When Jesus died and rested in death through the sabbath, he rose again on the third day, (Easter Sunday). The church fathers wrote that they chose to worship on Sunday as a celebration of Jesus's resurrection. Jesus killed our sin, which bound us in slavery to the flesh, by dying and staying dead through the sabbath, and he rose again on Sunday, raising us to life with him.

In this new life we received, we are no longer slaves to the flesh, and so we aren't subjected to the same kind of work that we were previously bound to. We continue to work (Col 3:23), but it is restful work under our new master. Jesus says, "my burden is light, and my yoke is easy" (Matt 11:28-30), and Paul wrote, "the peace of God which surpasses all understanding will guard your heart and mind" (Phil 4:7). The sabbath rest in the New Covenant is that spiritual rest in Jesus Christ, which we receive by the influence of the Holy Spirit in our hearts.

So Christians are called to observe the sabbath every day by resting in the comfort of our master, Jesus. His father, who has adopted us, provides for our every need (Matt 6:25-34), so that now rather than "living by the sweat on our brow" (Gen 3:19) in a cursed state of existence, we live in Christ as new creations, born again into spiritual purity and eternal life. So we have no worries; no concern; no struggle in this life, except to love our God in a way worthy of the name Christian.

"Either you're born twice and die once, or you're born once and die twice."