“The main objection against the perpetuity of this command is that the duty required is not moral. Those laws whose obligations arises from the nature of things and from the general state and nature of mankind, as well as from God’s positive revealed will, are called moral laws. Others, whose obligation depends merely upon God’s positive and arbitrary institution, are not moral: such as the ceremonial laws, and the precepts of the gospel about the two sacraments. Now, the objectors say, they will allow all that is moral in the decalogue to be of perpetual obligation. But this command, they say, is not moral.
But this objection is weak and insufficient for the purpose for which it is brought, or to prove that the fourth command, as to the substance of it, is not of perpetual obligation. For,
- If it should be allowed that there is no morality belonging to the command, and that the duty required is founded merely on arbitrary institution, it cannot therefore be certainly concluded that the command is not perpetual. We know that there may be commands in force under the gospel and to the end of the world, which are not moral. Such are the institutions of the two sacraments. And why may there not be positive commands in force in all ages of the church? If positive, arbitrary institutions are in force in gospel-times, what is there which concludes that no positive precept give before the times of the gospel can yet continue in force? But,
- As we have observed already, the thing in general that there should be certain fixed parts of time set apart to be devoted to religious exercises, is founded in the fitness of the thing, arising from the nature of things, and the nature and universal state of mankind. Therefore, there is as much reason that there should be a command of perpetual and universal obligation about this, as about any other duty whatsoever. For if the thing in general, that there be a time fixed, be founded in the nature of things, there is consequent upon it a necessity, that the time be limited by a command. For there must be a proportion of time fixed, or else the general moral duty cannot be observed.
- The particular determination of the proportion of time in the fourth commandment, is also founded in the nature of things, only our understandings are not sufficient absolutely to determine it of themselves. We have observed already that without doubt one proportion of time is in itself fitter than another, and a certain continuance of time fitter than any other, considering the universal state and nature of mankind, which God may see, though our understandings are not perfect enough absolutely to determine it. So that the difference between this command and others, does not lie in this (that other commands are founded in the fitness of the things themselves, arising from the universal state and nature of mankind, and this not), but only that the fitness of other commands is more obvious to the understandings of men, and they might have seen it of themselves. But this could not be precisely discovered and positively determined without the assistance of revelation.
So that the command of God, that every seventh day should be devoted to religious exercises, is founded in the universal state and nature of mankind, as well as other commands. Only man’s reason is not sufficient, without divine direction, so exactly to determine it. Though perhaps man’s reason is sufficient to determine that it ought not to be much seldomer, nor much oftener, than once in seven days.”
~Jonathan Edwards, “The Perpetuity and Change of the Sabbath”
Source and read more: http://www.biblebb.com/files/edwards/sabbath.htm