Calvin’s Catechism on the Fourth Commandment

166. Let us come to the fourth commandment.
Remember the Sabbath day, to keep it holy. Sis days shalt thou labour, and do all thy work: But the seventh is the Sabbath of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy man-servant, nor thy maid-servant, nor thy cattle, nor thy stranger that is within thy gates: For in six days the Lord made haven and earth, the sea, and all that in them is, and rested the seventh day, and hallowed it.

167. Does He order us to labour six days a week that may rest on the seventh?
Not precisely, but in allowing us to labour for six days, He excepts the seventh, on which it is not right to be engaged in work.

168. Does He thus forbid us all work one day a week?
This commandment has a particular reason, for the observance of rest is part of the ceremonies of the ancient Law, which was abolished at the coming of Jesus Christ.

169. Do you mean that this commandment properly belongs to the Jews, and that it was given for the time of the Old Testament?
I do, in so far as it is ceremonial.

170. How is that? Is there anything else in it besides the ceremony?
It was given for three reasons.

171. What are they?
To represent spiritual rest, in aid of ecclesiastical polity, and for the relief of servants.

172. What is this spiritual rest?
It is to cease from our own works, that the Lord may work in us.

173. How is that done?
By mortifying our flesh, that is, renouncing our own nature, so that God may govern us by His Spirit.

174. Is this to be done only one day a week?
This is to be done continually. After we have once begun, we must continue all our life.

175. Why, then, is a certain day appointed to represent this?
It is not required that the representation should be altogether identical with the truth, but it is sufficient that there should be some resemblance.

176. But why is the seventh day appointed rather than any other day?
The number seven implies perfection in Scripture. Thus it is suited to denote perpetuity. It reminds us also that our spiritual rest is only begun in this life, and will not be perfect until we depart from this world.

177. But what is meant when our Lord asserts that we must rest as He did?
After having created all His works in six days, He dedicated the seventh to the contemplation of His works. And in order better to induce us to do this, He set before us His own example. For nothing is so desirable as to be conformed to Him.

178. Must we meditate continually on the works of God, or is it sufficient on one day out of seven?
We must do it every hour, but because of our weakness, one day is specially appointed. And this is the polity of which I spoke.

179. What order, then, is to be observed on that day?
That the people meet to hear the doctrine of God, to engage in common prayer, and bear witness to their faith and religion.

Source: http://www.puritanboard.com/showthread.php/59385-Calvin-on-Having-to-Keep-the-Sabbath, Comment #4