God dealt with Nadab and Abihu so severely to teach us several things. (1) In His Church, His Word is Law; it may not be added to or subtracted from. He will not share His glory with another. (2) We worship a holy God, jealous for His Name, who will be worshipped only as He commands. (3) Good intentions, sincerity, religious preeminence and religious fervor do not excuse adding to or subtracting
from God’s Word. And (4) “[If] we reflect how holy a thing God’s worship is, the enormity of the punishment [of Nadab and Abihu] will by no means offend us.” 113. John Calvin, Commentaries on the Four Last Books of Moses, 3:431 (85)

Man is not to alter, edit or supplement what God has revealed for worship. (86)

In other words, regarding the worship of God, whatever He has not commanded is
forbidden! (90)

(1)“God is vitally concerned about the way He is worshipped.… He did not leave it to the ingenuity of man’s depraved mind to devise a worship system which would be acceptable to Him.”120 (2) “Man’s pride often leads to impertinence in worship.”121 (3) Disobedience to God’s directions for worship is sin and brings
punishment.…122
120. McCracken, “An Exposition of II Chronicles 26:16-21,” 77-78.
121. McCracken, “An Exposition of II Chronicles 26:16-21,” 78.
122. McCracken, “An Exposition of II Chronicles 26:16-21,” 80. (90)

First, the imposition of man-made liturgies in public worship.

Second, the introduction of holy-days in the church calendar.

Third, the use of vestments, or clerical garb, in worship.

Fourth, the use of the “altar call” in worship.

Fifth, the practice of coming forward and kneeling to receive the Lord’s Supper.
 (92-100)

(1) The first point to notice in this text [Deut. 13] is that this “prophet or dreamer of dreams” is not an open pagan idolater, he is a prophet, one who is supposed to be a mouthpiece of the Lord, who speaks only the Word of the Lord. ...
Second, this prophet may be able to perform “a sign or a wonder,” i.e., apparent miracles.
Third, he uses his power and office to lead the covenant people to another faith, to faith in other gods: “Let us go after other gods…and let us serve them.” ....
Fourth, the Lord uses this false prophet to accomplish His own purposes for His people. He is “testing you to find out if you love the Lord your God with all your heart and with all your soul.”   ....
Fifth, this prophet is a traitor to the covenant and to the covenant people, and is therefore to be arrested, tried, convicted and executed.....
Sixth, “testing is the prerogative of the Lord, not of man. Man has no right to test God, but God has every right to test man. Idolatry requires exposure, and the idolatry latent in the covenant people is tested and sifted out.”158  ....
Seventh, the key in distinguishing a covert spokesman of idolatry wearing the mask of a minister of God from a true minister of God is not the ability to do miracles; it is covenant faithfulness.  ....
Eighth, it is important to note that what is being condemned here is not heresy or wrong thinking about the Word of God, but the practice of idolatry, the teaching of idolatry and the encouraging of idolatry. ....
Ninth, this Biblical statute enforces the Second Commandment, because the condemnation of idolatry is so basic to the entire Biblical revelation....
Tenth, it is important for us to be clear on the nature of idolatry that is being forbidden and condemned in Deuteronomy 13. In verses 2, 6, 13, we are told that it is the sin of going and serving other gods. ...
158. Rushdoony, Law and Society, 463.    (107-109)

(2) First, “[i]t is the policy of the tempter to send his solicitations by the hand of those whom we love, whom we least suspect of any ill design upon us, and whom we are desirous to please and apt to conform ourselves to.”167
Second,
[i]t is our duty to prefer God and [the Christian] religion before the best friends we have in this world. 1. We must not, in complaisance to our friends, break God’s law (v.8) Thou shalt not consent to him, nor go with him to his idolatrous worship, no, not for company or curiosity… 2. We must not, in compassion to our friends, obstruct the course of God’s justice [“your eye shall not pity him, nor shall you spare or conceal him”]. He that attempts such a thing must not only be looked upon as an enemy, or dangerous person, whom one should be afraid of, and swear the peace against, but as a criminal or traitor, whom, in zeal for our sovereign Lord, his crown and dignity, we are bound to inform against, and cannot conceal… (v.9) 168
167. Henry, Matthew Henry’s Commentary on the Whole Bible, 1:609.
168. Henry, Matthew Henry’s Commentary on the Whole Bible, 1:609.     (113)

If it is idolatry to devise acts of worship that are not commanded by God in the Bible, how much more evil is it to impose idolatry on people by requiring them to perform the acts of worship originating in the brain of man rather than in God and inflicting them with church censure, ridicule or persecution for not doing so....To impose rites and acts of worship upon a church is to bind the conscience of the worshippers and to play God, for Christ alone is the Lord of the conscience. (114)

Kings are to obey and enforce God’s law, and the people are to obey those laws and
resist and seek to overturn all those laws not originating with God’s Law, and to disobey all those civil laws of the state which obedience to would demand disobedience to God, for “we must obey God rather than men.” (117)

When a tyrannical state or church government imposes acts of worship upon a people which are invented by men and not commanded by God in His Word—regardless of the threat and the punishment, even if it is death—Christians may not obey them....To submit to and use forms of worship so imposed upon us out of fear of persecution, ridicule or martyrdom is nevertheless idolatry. (117)

[T]o use any worship forms not commanded by God even forced upon us by the civil government or church on pain of death is idolatry and is forbidden to the covenant people of God. (119)

From Israel’s beginning as the Holy Nation, God commanded them to take measures to protect themselves from the risk of moral contagion. ...
The toleration of theological or ethical evil in the covenant community is suicidal.(122)

       Racheal

We not only have the responsibility to receive and observe the worship of God and its divinely revealed ordinances, we also are to keep pure and entire the worship of God and its ordinances. To keep them pure is to be constantly vigilant and to make the utmost effort to preserve God’s ordinances of worship from any and all mixture
with rites and practices invented by the brain of man and not commanded in the Word of God, for as John Knox said, “[a]ll worshipping, honouring, or service invented by the brain of man in the religion of God, without his own express commandment, is idolatry.”76 In keeping the worship of God pure we are “to allow or practice nothing but what is warranted by the rules which God has given us in his word; in opposition to those who corrupt his worship by intruding those ordinances into it which are of their own invention.”77 To keep them entire is, in faith, to practice diligently and regularly EVERYTHING God has commanded in His worship, leaving out not the smallest detail in its season, “so as that one duty may not justle out another,” “walking blamelessly in all the commandments and requirements of the Lord” (Luke 1:6). 
76. John Knox, Selected Writings of John Knox (ed. by David Laing; Edinburgh, 1895; reprint Dallas, TX: Presbyterian Heritage Publications, 1995), 23.
77. Ridgeley, Commentary on the Larger Catechism, 2:330.  (58-60)

We cannot keep the worship of God and the revealed ordinances of worship pure and entire for long unless we are faithful and diligent in the disapproving, detesting, opposing of all false worship. (63)

Paul was stirred emotionally when he saw the name of God so wickedly profaned, and His pure worship so corrupted, because nothing was more precious to him than the glory of God. This is the common response of all true Christians, that as soon as they see their God blasphemed, they are greatly vexed in their spirit, and are moved to do what they can to stop such blasphemy. (64)

Second, Paul was not so angry and grieving over the idolatry that he saw that he was driven to despair and discouragement with a defeated spirit, paralyzed to any effort to resist and seek to overturn the idolatry. Other men, angry at what they see, overwhelmed by the extensiveness and intensity of the idolatry would give up,
because they believe that all their efforts would be in vain. (65)

There can be no unity in the church, purity of worship with the blessing of God if believers “do not break off all the bonds of impiety, separate ourselves from idolaters, and keep ourselves pure and at a distance from all the pollutions which corrupt and vitiate the holy service of God… [because] after men in their folly have
once begun to make to themselves false gods, their madness breaks forth without measure, until they accumulate an immense multitude of deities.” 87. John Calvin, Commentary on the Book of Psalms, trans. by Rev. James Anderson, 5 vols. (Edinburgh: Calvin Translation Society; reprint Grand Rapids, MI: Baker Book House, 1979), 1:220. (65)

By monuments of idolatry, then, it is obvious that the Catechism, with Gillespie, is referring to: (1) Any monument dedicated in the past to the worship of idols that might preserve the memory of that idolatry or that might move people to return to that ancient idolatry; and (2) Those popish ceremonies obtruded upon the [Reformed and Presbyterian] Church of Scotland by the king of England and the Church of England, which were imitations of older rites and rituals of the Roman Catholic Church, for which no basis can be found in the Word of God as to their being commanded of God for us to use in His worship. This refers to such ceremonies as those set forth in the FIVE ARTICLES OF PERTH (1618) which were imposed upon the Church of Scotland by the English king: (1) Kneeling at Communion, (2) Observing holy days such as Christmas (which the Scottish Presbyterians saw as the idolatrous Saturnalia of the Romans adapted to become a popish festival), Easter, and Pentecost, (3) Episcopal Confirmation; (4) Private baptisms; and (5) Private administration of the Lord’s Supper.93 In fact, such ceremonies include any rite or liturgy in worship not commanded by the Word of God.
That it is the God-given duty of individuals, families, churches and states to remove all false worship and monuments to idolatry from a culture, according to each one’s place and calling, can be repeatedly shown from the Word of God. False worship, i.e., the worship of idols and the attempted worshipping of God by ways and means not commanded in His Word, is forbidden by God in the First and Second Commandments and is detestable to Him. Innovation in worship originating in the brain of man leads to tyranny in the state with laws imposed upon the populace originating in the brain of man, rather than the Law of God. (68-69)

The words, “shall be utterly destroyed,” are literally in Hebrew, “shall be put under the ban,” i.e., herem, which word denotes being devoted to God in death and “destroyed as execrable [detestable] and accursed, put to death without mercy.”95 Herem is a Hebrew word meaning “to utterly destroy,” “to devote to destruction,” “to place under a total curse,” “to ban.”  (70)

The lesson in the Herem principle is that toleration of evil in ourselves, our homes, our churches, our schools, our businesses, our courts, our communities, and our nations is intolerable, as well as displeasing to God. A society that tolerates evil collapses under the righteous judgment and anger of the God who “hates all workers of iniquity.” ..... Above all, we must be intolerant of the sin that remains within us. We must tear down the idols of our own hearts before we start tearing
down the altars of idolators. (71-72)

[A]ll monuments of idolatry, i.e., everything that has been notoriously abused by idolatry, are to be abolished for two reasons: they remind and they move.
First, they remind, i.e., they preserve the memory of idols in people’s minds.
....
Second, they move, i.e., such reminders of idolatry often move people to turn back to idolatry from the worship of the true God. These reminders not only allow the memory of the superstitions they represent to continue among people, but many times that memory, imagination and curiosity seduce people to resume the superstition and the idolatrous use of them. (79-80)

     Racheal