Remembering the Sabbath day is indeed the Third Commandment, according to the Roman Catholic and Lutheran enumeration. But according to the original enumeration in Exodus 20 and Deuteronomy 5, it is the Fourth.
The Catholic and Lutheran numbering comes from virtually dropping the Second Commandment, “Thou shalt not make unto thee any graven image… thou shalt not bow down thyself to them, nor serve them…” (Exodus 20:4-6, Authorized Version).
By omitting the Second Commandment from the Ten, the succeeding commandments become renumbered so that the Third becomes the Second and the Fourth becomes the Third, and so on. The Tenth Commandment is then divided into two separate commandments — coveting your neighbor’s wife and coveting your neighbor’s goods — to fill in the gap (My Catholic Faith, by Louis LaRavoire Morrow, page 194).
The Bible, however, gives no precedent for dividing this one commandment into two. Jesus referred to just one commandment against coveting in Luke 12:15, and the apostle Paul wrote: “I would not have known sin except through the law. For I would not have known covetousness unless the law had said, ‘You shall not covet’ ” (Romans 7:7).
It is not logical to divide the first two points of the Tenth Commandment (coveting one’s neighbor’s house and coveting his wife) into two separate commandments while ignoring the four other items mentioned (manservant, maidservant, and donkey and ox). The overall principle of not coveting anything of one’s neighbor’s (the last point stated in the Tenth Commandment) adequately covers all potential situations (Exodus 20:17).
Source: The Good News, August 1985