Consulting Scripture and The Book of Common Prayer, I've written previously on why Sunday is not the Sabbath. After recently reading a couple of posts on other blogs ("Sabbath/Day of Rest Changed to Sunday"and "The Changing of the Sabbath From Saturday to Sunday - Catholic Authority in Action"), I think this is a topic worth revisiting.
This time, I'll let Shannon Johnston address the matter. When he was rector of All Saints' Episcopal Church in Tupelo, MS (he is now the bishop coadjutor for the Episcopal Diocese of VA), Shannon wrote a parish newsletter article entitled: "Now Hear This! 'First' is Not the Same as 'Seventh.' 'Feasting' is Not the Same Thing as 'Abstaining.' Sunday is Not the Sabbath!" [The Cross and Crown, 7/21-7/28/2002]. Below is an excerpt.
Obviously, the "Sabbath day" is rooted in Jewish worship and law. Since the Hebrew Scriptures are part of our faith, Christians are free to observe the Sabbath - not under law but through choice. But, so choosing, it is to be kept on Saturday. The Sabbath is defined as a "day of rest," and thus is inextricably bound throughout all Holy Scripture to the seventh day of Creation - when God rested from all He had done. Scripture is equally clear that Sunday is the first day of the week, and that when the first Christians gathered on Sunday, they were not keeping the Sabbath, but were commemorating the Resurrection; they were not observing the Day of Rest, but rather, the Day of the Lord.
The Sabbath is also the day set apart for Jewish worship, not just rest. Likewise, Sunday is the day Christians have set apart for worship. Is it not natural and appropriate, therefore, to think of Sunday in like terms as "sabbath"? Of course, the parallel of worship is clear, but Sunday is not so much a ‘day of rest’ (implicit in "sabbath day") as it is a day of celebration. It is the day of recreation, being especially mindful of that word’s origin, re-creation, which is what Jesus did for us. We may indeed ‘celebrate’ and renew by resting, but we may also do so by feasting and (for want of a better term) merry-making. … Sunday is a feast day for Christians; it is not a day of "abstinence." …
What the Sabbath and Sunday have in common is that they are the days specifically set apart for particular attention to our relationship with God. But the essential character, "psychology," and theology of these two days is fundamentally different.