Q. 103. What doth God require in the fourth commandment?
First, that the ministry of the Gospel and the schools be maintained; and that I, especially on the Sabbath, that is, on the day of rest, diligently frequent the church of God, to hear His Word, to use the sacraments, publicly to call upon the Lord, and contribute to the relief of the poor, as becomes a Christian. Secondly, that all the days of my life I cease from my evil works, and yield myself to the Lord, to work by His Holy Spirit in me: and thus begin in this life the eternal Sabbath.
 Deuteronomy 12:19; Titus 1:5; 1 Timothy 3:14–15; 1 Corinthians 9:11; 2 Timothy 2:2; 1 Timothy 3:15;  Leviticus 23:2;  Acts 2:42, 46; 1 Corinthians 14:19, 29, 31; 1 Corinthians 11:33;  1 Timothy 2:1;  1 Corinthians 16:2;  Isaiah 66:23.
The Heidelberg Catechism is an excellent catechism, especially for its warmth and devotional expression of Reformed theology. However, we should realise that it does differ from the Westminster Standards at a couple of points, one of which being on the treatment of the Fourth Commandment. The Heidelberg Catechism follows the Continental view of the Christian Sabbath, which essentially teaches that it is not obligatory for Christians to sanctify one whole day in seven as a holy Sabbath unto the Lord. This Continental view is not extremely apparent at the first reading of the answer to Q/A. 103. However, we can see it if we think carefully about the second part of the answer, viz.: “that all the days of my life I cease from my evil works, and yield myself to the Lord, to work by His Holy Spirit in me: and thus begin in this life the eternal Sabbath.” The exposition follows closely Calvin’s remark that “the purpose of [the Fourth] commandment is that, being dead to our own inclinations and works, we should meditate on the Kingdom of God, and that we should practise that meditation in the ways established by him” (ICR 2.8.28). According to Calvin, although the Fourth Commandment designates a stated day of public worship and prescribes a day for bodily rest, its main purpose is to serve as a foreshadowing of the spiritual rest enjoyed by believers. With all due respect, we believe Calvin to be in error at this point. Jonathan Edwards seems to have Calvin’s view of the Sabbath in mind when he says:
Some say, that the fourth command is perpetual, but not in its literal sense; not as designating any particular proportion of time to be set apart and devoted to literal rest and religious exercises. They say, that it stands in force only in a mystical sense, viz. as the weekly rest of the Jews typified spiritual rest in the Christian church; and that we under the gospel are not to make any distinction of one day from another, but are to keep all time holy, doing everything in a spiritual manner.
But this is an absurd way of interpreting the command as it refers to Christians. For if the command be so far abolished, it is entirely abolished. For it is the very design of the command, to fix the time of worship. The first command fixes the object, the second the means, the third the manner, the fourth the time. And if it stands in force now only as signifying a spiritual, Christian rest, and holy behaviour at all times, it doth not remain as one of the ten commands, but as a summary of all the commands (“The Perpetuity and Change of the Sabbath,” in Works 2.95).
We are compelled to agree with Edwards! The day which must be kept as the Sabbath by Christians is now the first day of the week since Christ rose from the dead on the first day of the week (cf. Ps 118:22–24). The Fourth Commandment, moreover, is morally, universally and perpetually obligatory upon all men until it finds fulfilment in the eternal heavenly rest of the children of God. In the mean time, all men have a duty to set aside the whole of the first day of the week as a day of rest and worship.
Heidelberg Catechism >