My mom and I talked about it last night, and she suggested doing a retreat on the Sabbath, so we could study it.

this is an ambiguous sentence (is “on” about the subject or the timing of the retreat?). of course he meant subject. but if we think timing, isn’t it exactly right? and after all, study, especially of God’s word and commandments, is the time-honored activity for the Sabbath.

Might we hold worship services to begin and end Sabbath time?

i think the answer is “yes”, but the Sabbatarianism of your suggestion that it must be Saturday and not Sunday misses the point, or at least, it misses about half the new testament. The point, it seems to me, isn’t so much about the day, but about the way it’s spent.

Christian tradition suggests that Sunday is indeed the day we should spend in this way, and the canons of our church seem to agree: “All persons within this Church shall celebrate and keep the Lord’s Day, commonly called Sunday, by regular participation in the public worship of the Church, by hearing the Word of God read and taught, and by other acts of devotion and works of charity, using all godly and sober conversation.”

I believe that our Sabbath keeping must be a Christian Sabbath keeping. Hence the canon’s mention of “works of charity.” I don’t believe the use of the term “works” here is an accident, and I am reminded of Jesus’ insistence that works of charity are exactly right for the Sabbath, no matter what Jewish tradition said. These must be our cues.

So yes, let’s mark it with liturgy! How about evening prayer on Saturday, morning prayer and Eucharist on Sunday, and evening prayer on Sunday? The necessary liturgies are already there, waiting to be used for just this purpose.

And then, such things as vestry meetings and weekly shopping might best be avoided, but working on the local Habitat for Humanity project would be exactly right.