A law or a commandment being positive moral law in no way diminishes the fact that it is binding and obligatory. Hopkins writes concerning the specific day that it “is from his positive will and command, and therefore is as binding and forcible as if it were a law of nature engraven on our hearts; unless the same authority alters it that did first enjoin it. For this being a positive law, is therefore good and necessary, because commanded.” Robert Dabney writes that the worship of God should also have a public and corporate aspect of it, which necessitates a specific day:
That it is man’s duty to worship God, none will dispute. Nor will it be denied that this worship should be in part social; because man is a being of social affections, and subject to social obligations; and because one of the great ends of worship is the display of the Divine glory before our fellow creatures. Social worship cannot be conducted without the appointment of a stated day; and what more reasonable than that the Divine authority, who is the object of this worship, should meet this necessity, by Himself fixing the day for all mankind?
There is nothing inherently (in and of itself) moral about the seventh or first days of the week. What makes one day moral and obligatory is the command of God. Now we move to the more controversial part concerning the nature of the Sabbath.
What does it mean that the Sabbath commandment is moral? It basically means that it is eternal and cannot be abrogated. This is the Confessional description: a positive moral, and perpetual commandment. A commandment that will not go away in its essence and is ever-binding. The day is a positive command as we’ve tried to explain, which can be changed if the Lord so pleases. But the essence of the Sabbath, which is rest and worship, is demanded by the law of nature and is binding upon all men. A lot of Christians in the present time, which profane the Sabbath Day, contend that the Sabbath is merely and essentially ceremonial and not moral. In this way, they justify the abrogation or “fulfillment” of the Sabbath under the New Covenant. It is essential to this viewpoint that they understand the Sabbath as merely a positive command given at Sinai, not as we tried to prove, an institution from the seventh day of the world.
That the Sabbath is essentially moral (we don’t deny that there are ceremonial and temporary aspects more on which see below) is seen in the fact that it was instituted even before the Fall on the seventh day. It was “made for man” as our Lord taught us (Mark 2:27, see here). It was a gift from God given to Adam and to all his posterity, even before the Fall. Moreover, the Sabbath was moral in that it was based upon the Creator’s example. The Sabbath was instituted and based on what God did. Six days of work; seventh day of rest. Therefore, man was commanded to keep the Sabbath by following his Creator’s example. This is part of what it means to be in the Imago Dei. The words of Ezekiel Hopkins are very helpful here:
This declaration, if the will of God concerning the sanctification of the Sabbath is attended with a moral reason; and therefore is not merely and barely positive, as ceremonial laws are. The reason is, that God rested on the seventh day; and therefore we ought so to...