I. The Definition, Nature, and Properties of God's Law
"Law now, in general, is a rule, or precept, commanding things honest and just, requiring obedience from creatures endowed with reason, with a promise of reward in case of obedience, and with a threatening of punishment in case of disobedience." [Zacharias Ursinus - Commentary on the Heidelberg]
"By the law of God is meant the commandments which God, the Creator, and Supreme King, and Lawgiver, hath laid upon all the children of men, his creatures and subjects, as the rule of their obedience." [Thomas Vincent - The Shorter Catechism]
"the law of heaven being enacted for our minds, the first thing necessary to a due observance of the Law is to put them under restraint." [John Calvin - Institutes]
"The moral law itself is αὐτοπιστος, it rests in itself, it is like the sun which is seen only by its own rays; it depends on no proof and reasoning; it is mighty because it is there, posits and maintains itself; its power consists in its authority, in the divine majesty with which it makes its: thou shalt, be heard in our conscience." [Herman Bavinck - Reformed Dogmatics]
"The law is that which binds the conscience." [Charles Hodge - Systematic Theology]
"The only rule which God hath given us, according to which our whole obedience unto him must be guided, is his revealed will." [Thomas Vincent - The Shorter Catechism]
"Our obedience must correspond with the Word, as the copy with the original. To seem to be zealous, if it be not according to the Word, is not obedience—but will-worship." [Thomas Watson - The Ten Commandments]
"God foreseeing that the Israelites would not rest, but after receiving the Law, would, unless sternly prohibited give birth to new kinds of righteousness, declares that the Law comprehended a perfect righteousness." "All which is attributed to it is, that it commands what is right, prohibits crimes, holds forth rewards to the cultivators of righteousness, and threatens transgressors with punishment, while at the same time it neither changes nor amends that depravity of heart which is naturally inherent in all." [John Calvin - Institutes]
II. The Threefold Division: Moral, Ceremonial, and Judicial Law
"The divine law is ordinarily divided, or considered as consisting of three parts; the moral, the ceremonial and the judicial." [Zacharias Ursinus - Commentary on the Heidelberg]
"1. There is the judicial law, which concerned chiefly the nation of the Jews, and in every respect doth not bind all other nations. 2. There is the ceremonial law, which was in no part of it binding upon any, but for a time; namely, before the coming of Christ, who fulfilled this law, and abrogated it. 3. There is the moral law, written at first by God himself, on tables of stone; which is a standing rule of obedience unto the end of the world." [Thomas Vincent - The Shorter Catechism]
"The moral law is a doctrine harmonising with the eternal and unchangeable wisdom and justice of God, distinguishing right from wrong, known by nature, engraven upon the hearts of creatures endowed with reason in their creation, and afterwards often repeated and declared by the voice of God through his servants, the prophets; teaching what God is and what he requires, binding all intelligent creatures to perfect obedience and conformity to the law, internal and external, promising the favor of God and eternal life to all those who render perfect obedience, and at the same time denouncing the wrath of God and everlasting punishment upon all those who do not render this obedience, unless remission of sins and reconciliation with God be secured for the sake of Christ the mediator."
"Ceremonial laws were those which God gave through Moses in reference to ceremonies, or the external solemn ordinances which were to be observed in the public worship of God, with a proper attention to the circumstances which had been prescribed; binding the Jewish nation to the coming of the Messiah, and at the same time distinguishing them from all other nations; and that they might also be signs, symbols, types and shadows of spiritual things to be fulfilled in the New Testament by Christ."
"The judicial laws were those which had respect to the civil order or government, and the maintenance of external propriety among the Jewish people according to both tables of the Decalogue; or it may be said that they had respect to the order and duties of magistrates, the courts of justice, contracts, punishments, fixing the limits of kingdoms, &c. These laws God delivered through Moses for the establishment and preservation of the Jewish commonwealth, binding all the posterity of Abraham, and distinguishing them from the rest of mankind until the coming of the Messiah..."
"The moral law is known naturally, binds all men, and that perpetually; it is different, however, with the ceremonial and judicial law."
III. The Law Written on the Heart (Natural Law) and the Decalogue
"The Decalogue contains the sum of the moral laws which are scattered throughout the Scriptures of the Old and New Testaments. The natural, and moral law were the same in man before the fall, when his nature was pure and holy. Since the fall, however, which resulted in the corruption and depravity of our nature, a considerable part of the natural law has become obscured and lost by reason of sin, so that there is only a small portion concerning the obedience which we owe to God still left in the human mind. It is for this reason that God repeated, and declared to the church the entire doctrine and true sense of his law, as contained in the Decalogue. The Decalogue is, therefore, the renewal and re-enforcing of the natural law, which is only a part of the Decalogue." [Zacharias Ursinus - Commentary on the Heidelberg]
"Moreover, the very things contained in the two tables are, in a manner, dictated to us by that internal law, which, as has been already said, is in a manner written and stamped on every heart." [John Calvin - Institutes]
"That moral law was known to Adam by nature and therefore did not need, like the probationary command, to be revealed in a special way. In essence it is like the ten commandments, but nevertheless bore another form, for the law given on Sinai presupposes sins and therefore speaks almost always negatively: thou shalt not, and the moral law before the fall was much more positive." [Herman Bavinck - Reformed Dogmatics, Vol. 2]
"Though without the light of the Scriptures there cannot be so clear a discovery of the moral law, yet by the light of nature it is made known unto all nations in some measure, sufficient to leave the very heathen without excuse for their disobedience." [Thomas Vincent - The Shorter Catechism]
"This is still more apparent from what the Bible teaches of the law as written on the heart. The Apostle tells us that those who have a written revelation, shall be judged by that revelation; that those who have no externally revealed law, shall be judged by the law written on the heart. That the heathen have such a law, he proves first, from the fact that 'they do by nature the things contained in the law'" [Charles Hodge - Systematic Theology]
IV. The Perfect Demands of the Law and the Inability of Fallen Man
"The answer given by the unsophisticated and enlightened conscience of men, and by the word of God, is that the law demands complete perfection, or the entire conformity of the moral nature and conduct of a rational creature with the nature and will of God. ... It includes the entire absence of all sin, and the entire conformity of nature to the image and will of God." [Charles Hodge - Systematic Theology]
"The Decalogue demands in every commandment internal and external obedience in the understanding, will, heart and actions of the life, perfect not only as to the parts, but also as to the degrees of this obedience..." [Zacharias Ursinus - Commentary on the Heidelberg]
"For the law demanding perfect love condemns all imperfection, unless its rigor is mitigated." [John Calvin - Institutes]
"To obey the law in a legal sense—to do all the law requires—no man can. Sin has cut the lock of original righteousness, where our strength lay." [Thomas Watson - The Ten Commandments]
"The nature of man in its corrupt state since the fall, is entirely unable to fulfill what the law demands; yea, it cannot so much as commence acceptable obedience to God..." [Zacharias Ursinus - Commentary on the Heidelberg]
"perfect obedience is impossible, and life thereby is unattainable; therefore the law was not given unto man after his fall that it might give life." [Thomas Vincent - The Shorter Catechism]
"We readily admit, therefore, that the perfect obedience of the law is righteousness, and the observance of any precept a part of righteousness, the whole substance of righteousness being contained in the remaining parts. But we deny that any such righteousness ever exists. Hence we discard the righteousness of the law, not as being in itself maimed and defective, but because of the weakness of our flesh it nowhere appears."
"The righteousness of the law consists in the perfection of works; but no man can boast of fulfilling the law by works, and, therefore, there is no righteousness by the law." [John Calvin - Institutes]
V. The Abrogation and Perseverance of the Law (The Threefold Use)
"The moral law, however, has not been abolished as it respects obedience, but only as it respects the curse, justification and constraint." [Zacharias Ursinus - Commentary on the Heidelberg]
"In some sense it is abolished to believers. (1) In respect of justification. They are not justified by their obedience to the moral law. Believers are to make great use of the moral law—but they must trust only to Christ's righteousness for justification; as Noah's dove made use of her wings to fly—but trusted to the ark for safety." "The moral law is abolished to believers, in respect of its curse. They are freed from its curse and condemnatory power."
"But though the moral law be thus far abolished, it remains as a perpetual rule to believers. Though it be not their Savior , it is their guide . Though it is not a covenant of life; yet it is a rule of life. Every Christian is bound to conform to it; and to write, as exactly as he can, after this copy." [Thomas Watson - The Ten Commandments]
"Though believers, through their interest in Christ, are delivered from the curse and condemnation, the rigour and irritation, of the moral law, which, whilst out of Christ, they are under, yet the moral law is still of singular use unto believers, to provoke them unto thankfulness for Christ, who hath fulfilled the law in their stead; and to be a rule according to which they ought to endeavour, as much as may be, to order their hearts and lives, however in this life perfection of obedience thereunto is unattainable." [Thomas Vincent - The Shorter Catechism]
"What Paul says, as to the abrogation of the Law, evidently applies not to the Law itself, but merely to its power of constraining the conscience. For the Law not only teaches, but also imperiously demands. If obedience is not yielded, nay, if it is omitted in any degree, it thunders forth its curse."
"The third use of the Law (being also the principal use, and more closely connected with its proper end) has respect to believers in whose hearts the Spirit of God already flourishes and reigns. ... The Law acts like a whip to the flesh, urging it on as men do a lazy sluggish ass. Even in the case of a spiritual man, inasmuch as he is still burdened with the weight of the flesh, the Law is a constant stimulus, pricking him forward when he would indulge in sloth." [John Calvin - Institutes]
"The usus politicus and the usus paedagogicus of the law have only accidentally become necessary through sin; even if these fall away, the principal usus, the usus didacticus, normativus remains. The law is after all expression of God’s being; Christ as man was of himself for himself subject to the law; Adam before the fall had the law written in his heart; in the believer it is again engraved on the tables of his heart by the H. Spirit; and in heaven all will walk according to the Lord’s law. The gospel is temporary but the law is eternal and is precisely restored by the gospel." [Herman Bavinck - Reformed Dogmatics, Vol. 4]
VI. The Distinct Functions and Harmony of Law and Gospel
"The law was engraven upon the heart of man in his creation, and is therefore known to all naturally, although no other revelation were given. ... The gospel is not known naturally, but is divinely revealed to the Church alone through Christ, the Mediator."
"The law teaches us what we ought to be, and what God requires of us, but it does not give us the ability to perform it, nor does it point out the way by which we may avoid what is forbidden."
"The law promises life to those who are righteous in themselves, or on the condition of righteousness, and perfect obedience. ... The gospel, on the other hand, promises life to those who are justified by faith in Christ, or on the condition of the righteousness of Christ, applied unto us by faith." [Zacharias Ursinus - Commentary on the Heidelberg]
"law and gospel, considered in concreto, do not differ so much in that the law always appears in commanding and the gospel in promising form, for the law also has promises, and the gospel admonitions and obligations. But they differ especially in content: the law demands that man work out his own righteousness and the gospel invites him to renounce all self-righteousness and to accept that of Christ and to that end even grants the gift of faith."
"every man is not first by the gospel but is by nature obligated by the law to believe God on his word and thus also to accept the gospel, in which He speaks to man. Therefore the gospel from the outset lays claim to all men, binds it in their conscience, for that God who speaks in the gospel is no other than he who has made himself known to them in his law." [Herman Bavinck - Reformed Dogmatics, Vol. 4]
"He has maintained its majesty and glory; and faith does not nullify the law but confirms it, Rom. 3:31." [Herman Bavinck - Reformed Dogmatics, Vol. 3]