After the Second, it is probably the Fourth Commandment that has received the most attention by historians, because it outlines what became one of the key priorities of Protestant (and specifically Puritan) piety: the observation of the Sabbath. The Fourth Commandment was also the longest in the Decalogue:
Remember the sabbath day, to keep it holy. Six days shalt thou labour, and do all thy work: But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it.
The Sabbath was a potentially controversial and complex notion for several reasons. As it had been instituted for the Jewish people in the Old Testament, the Saturday Sabbath was counted as part of the Ceremonial Law along with other ritual aspects of Judaism, such as the dietary requirements that forbade the eating of pork and shellfish. Christian doctrine held that this Ceremonial Law had been abrogated – superseded and therefore rendered obsolete – by the coming of Christ. Many aspects of Judaism were considered to foretell important features of Christianity, such as the welcoming of male infants into the Jewish faith and community through infant circumcision as a foreshadowing of the spiritual induction into the Christian community provided by the sacrament of baptism. Once Christ had come to earth and sacrificed himself, these weak glimmers of true religion were replaced by the blinding light of the gospel.
Early Christians had therefore begun to observe the Sabbath on a Sunday, as a mark of difference from Judaism, and Reformed Protestants maintained this practice, in spite of isolated suggestions like that by John Frith in 1533 to move the Sabbath to a Tuesday, to avoid any charges of continuity with Catholic practice. In the main, Protestants squared the circle by maintaining that while the external details of the Sabbath (such as when it was to be held) were ceremonial (and therefore non-binding) issues, the necessity of resting from work and worshipping God one day in Seven was a binding imperative of God’s Moral Law (another term for the Ten Commandments), which remained mandatory for all Christians for all eternity.
John Dod, whose blockbuster Plaine and familiar exposition of the Ten Commandements went through twenty editions between 1603 and 1662, discussed the precept at length, one section at a time. His summary was fairly pithy, however; this was the commandment ‘to teach us, to set apart the seventh day wholly, from all worldly affairs, to the exercises of Religion and mercy’. Dod discussed the moral, binding nature of the commandment, stating baldly that ‘we may easily perceive, that this Commandment is no more ceremoniall then all the rest’. The injunction to Remember the Sabbath functioned as a special memorandum to keep the commandment in view of man’s infirmity and readiness to be drawn from God’s service.
Not do any manner of work was an essential ingredient of the Sabbath, and to make that point, Dod discussed extensively the example of the man described in Numbers 15 as found outside the camp gathering sticks on the Sabbath day. This had been such ‘an ill example of libertie to others’ that although ‘he did the smallest worke, yet that little worke was so great sinne, that God appoints him to be stoned to death for it.’
The actual works to be undertaken on the Sabbath were fairly uncontentious, although the precise formulation of dos and don’ts varied according to author: for Dod, in addition to attending Church services, the godly ought to meditate on God’s word and works, read the word/hear the word read, pray, sing psalms, enter godly conference, and perform the works of mercy enjoined by the bible. The faithful had not only to perform these works, but to delight in them, and spend the whole 24 hours of the Sabbath engaged in them, forbearing worldly business and thoughts. Some authors went much further than Dod, suggesting that the God-ward attitude of the Sabbath ought to permeate the entirety of the life of the Christian, proposing multiple or perpetual Sabbaths, or extending it to include lengthy pre-Sabbath preparations. Not only did this bring the Fourth Commandment dangerously close to the common view of the Third, but Dod had an additional warning: ‘and these men that among us urge so much, that every day must be a Sabbath: marke them, whether they rest from sin an y day at all, and observe if there be anie families, so bad as theirs’!
 E.G. Kenneth Parker, , The English Sabbath: A study of doctrine and discipline from the Reformation to the Civil War (Cambridge: Cambridge University Press, 1988).
 As recently described in Karl Gunther, Reformation Unbound: Protestant Visions of Reform in England, 1525-1590 (Cambridge: CUP, 2014), p. 1.
 John Dod, A plaine and familiar exposition of the Ten commandements (1604), STC2: 6968, p. 124.