The Westminster Shorter Catechism
Q41. Where is the moral law summarily comprehended?
A. The Moral Law is summarily comprehended in the Ten Commandments.[1]
[1] Deuteronomy 10:4; Matthew 19:17.
The Moral Law of God reflects the holy character of God and teaches us how we ought to act and think with regards to God and man. This Law was written in the heart of man, he being created in the image of God. But because of the fall, this knowledge was partly lost. It then became necessary for God to re-issue the Law. This, He did in the Ten Commandments or the Decalogue which, unlike all other of Gods commandments, was issued with a special and awesome introduction (Ex 19:1622); was spoken directly to the people (Ex 20:1, 19); was personally inscribed by God Himself on two tablets of stone (Ex 24:12; 31:18; 32:16; 34:1, 28); and was alone placed inside the ark (Ex 25:16; Heb 9:4). The fact that such special dignity and honour are assigned to these commandments as distinct from all other commandments in the Old Testament indicates that they are of different nature from the other laws, they being alone perpetual and universal. Moreover when the content of the Decalogue is examined, it can be seen to have an apodictic character, i.e., it is general and applicable in all situations; unlike the Civil and Ceremonial Laws which are casuistic, i.e., are applicable only within specific situational, geographic or temporal boundaries.
The Ten Commandments are, furthermore, all encompassing, so that: (1) All the
Laws in the Bible which are of moral or ethical character may be reduced to one
or more of the precepts; (2) Whatever sin
is forbidden in any one precept, the contrary duty is commanded, and all sins
of the same kind also are forbidden; and not only the outward act, together
with the words and gestures tending thereunto, but also all the inward
affections to sin, together with all causes, means, occasions, appearances, and
whatever may be a provocation unto it, either in ourselves or others (Thomas Vincent);
(3) Whatever duty is commanded, the contrary is forbidden; and all duties of
the same kind are included, together with all suitable affections thereunto, as
also the using all means appointed for help, quickening, and furtherance
therein, and our endeavours in our places to help and further others in their
obedience (T. Vincent).
It is because of the special character of the Decalogue, that most Reformed
catechisms contain an exposition of it, and it is a feature of Reformed
theology that Christians are still obliged to keep the Decalogue because God is
holy and we are commanded to be holy as He is holy (cf. 1 Pet 1:16), and
because without holiness, no man shall see the Lord (Heb 12:14). Keeping the
Law does not justify, but our sanctification involves our obedience to the Law.
We must also remember that the duty to keep the Law is not legalism. Legalism
arises only when the Law of God is ignored and human rules and regulations are
set in place for Christians to follow. In other words, legalism usually arises
out of antinomianisma failure to give the Law of God its proper place and
obedience.