That’s a great question, and I love the implication of the question, namely, that the Sabbath did change. Part of the problem we face in our time is a lot of people think the Sabbath is entirely passé.
One place I’d begin is with Revelation 1:10 where John says, “I was in the Spirit on the Lord’s day.”
For those who think that the Sabbath is completely ended with the coming of Jesus and that “all days are alike” in the new covenant (Rom. 14:5), they misuse a statement of Paul. The fact that John says there is a “Lord’s day” in the new covenant shows there is a day set apart in a unique way for the Lord. And so that’s a place to begin.
I think Colossians chapter 2, which talks about the Sabbath being past, shows that the old Sabbath—the “Sabbaths” literally in Greek (Col. 2:16)—are passed away. And then we look at the Apostolic practice of frequently meeting on the first day, and we begin to see this pattern emerging from the New Testament: that whereas Jews rested on the seventh day, Christians rest and worship on the first day.
Then I think theologians have helpfully theologized that. They said that when God created the world He gave all mankind—not just His people, but all mankind before the fall—the Sabbath day to establish a pattern of work and then rest. But with the coming of Christ that pattern changes, because Christ has brought that ultimate rest to us. So we begin with rest, and then we work out of that rest. And I think that’s a really helpful way of thinking about why God changed this so that the resurrection of Christ is absolutely central in the life and experience of the church.