Westminster Shorter Catechism q&a's 49-52.
Q. 49. Which is the second commandment? A. The second commandment is, [Thou shalt not make unto thee any graven image, or any likeness of any thing, that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; thou shalt not bow down thyself to them, nor serve them: For I the Lord thy God am a jealous God, visiting the iniquities of the fathers upon the children, unto the third and fourth generation of them that hate me, and shewing mercy unto thousands of them that love me, and keep my commandments.]
Q. 50. What is required in the second commandment? A. The second commandment requireth, the receiving, observing, and keeping pure and entire all such religious worship and ordinances, as God hath appointed in his word.
Q. 51. What is forbidden in the second commandment? A. The second commandment forbiddeth the worshipping of God by images, or any other way not appointed in his word.
Q. 52. What are the reasons annexed to the second commandment? A. The reasons annexed to the second commandment, are God’s sovereignty over us, his propriety in us, and the zeal he hath to his own worship.
From John Flavel we read:
Q. 1. What is the sin especially forbidden in the second commandment? A. The sin here forbidden, is the corruption of God’s worship, by making any similitude of any person in the Godhead, and performing divine worship before it, or to it; Exodus 32:8. They have turned aside quickly out of the way which I commanded them: They have made them a molten calf, and have worshipped it, and have sacrificed thereunto, and said, these be thy gods O Israel, which have brought thee up out of the land of Egypt. Deuteronomy 4:15-16. Take ye therefore good heed unto yourselves (for ye saw no manner of similitude on the day that the Lord spake unto you in Horeb, out of the midst of the fire) lest ye corrupt yourselves and make you a graven image, the similitude of any figure, the likeness of male or female.
Q. 2. What is the second sin forbidden in this commandment? A. The second sin against this commandment is will-worship, consisting in the addition of man's inventions to the worship of God, as a part thereof; Matthew 15:9. But in vain they do worship me, teaching for doctrines the commandments of men. Colossians 2:20-23. Whereof if ye be dead with Christ from the rudiments of the world, why, as though living in the world, are ye subject to ordinances. (Touch not, taste not, handle not, which all are to perish with the using) after the commandments and doctrines of men? Which things have indeed a shew of wisdom in will-worship and humility, and neglecting of the body, not in any honour to the satisfying of the flesh.
Q. 3. But if those additions be for the more decent worshipping of God, is it not allowed by 1 Corinthians 14:40. Let all things be done decently, and in order? A. No; that scripture commands that God’s institutions be regularly and decently performed, but not that we invent ceremonies that are symbolical, to make them more decent than Christ left them.
Q. 4. Why is the second commandment left out in all the public offices of the popish church? A. Because it expressly condemns their idolatrous images, kneeling at the sacrament, prayers to saints, and all their superstitious crosses, surplices, and chrisme, as sinful.
Q. 5. Do they not clear themselves from idolatry, by telling us they only worship God before, or by them, but not the images themselves? A. No, they do not; for the use of images in God’s worship is expressly condemned in this commandment; as if this would excuse the papists, it had also excused the Israelite in worshipping the calf, Exodus 32:4. And they said, These be thy gods, O Israel, that brought thee out of the land of Egypt.
Q. 6. What is the first reason annexed to the second commandment? A. The first reason annexed is God’s sovereignty, I the Lord; which shews that it belongs to God only to institute his own worship, and make it effectual; and therefore to do that in his worship which he never commanded, is sinful and dangerous; Jeremiah 7:31. And they have built the high places of Tophet, which is in the valley of the son of Hinnom, to burn their sons and their daughters in the fire, which I commanded them not, neither came it into my heart.
Q. 7. What is the second reason annexed to the second commandment? A. The second reason is God’s propriety in us: He is our God, and we belong to him; and therefore to corrupt his worship, greatly aggravates our sins; Hosea 9:1. Rejoice not, O Israel, for joy, as other people; for thou hast gone a whoring from thy God, &c.
Q. 8. What is the third reason annexed to the second commandment? A. The jealousy of God over his worship and worshippers; so that this sin of corrupting his worship will dreadfully incense his wrath, as it did, Leviticus 10:1-2. And Nadab and Abihu, the sons of Aaron, took either of them his censer, and put fire thereon, and offered strange fire, before the Lord, which he commanded them not. And there went out fire from the Lord, and devoured them, and they died before the Lord.
Q. 9. What is the first instruction from the second commandment? A. That it is an heinous sin to neglect the worship of God in that manner he hath appointed us to worship him, as in prayer; Jeremiah 10:25. Pour out thy fury upon the heathen that know thee not, and upon the families that call not on thy name. Hearing the word; Proverbs 28:9. He that turneth away his ear from hearing the law, even his prayer shall be abomination.
Q. 10. What is the second instruction from the second commandment? A. That those who suffer for endeavouring to preserve the purity of God’s ordinances, and nonconformity to the contrary injunctions of men, have a good warrant to bear them out in all such sufferings; Deuteronomy 4:2. Ye shall not add unto the word which I command you, neither shall you diminish ought from it, that ye may keep the commandments of the Lord your God, which I command you.
Q. 11. What is the third instruction from the second commandment? A. That it is highly sinful and dangerous to innovate and prescribe by human authority such symbolical rites in the worship of God, as he never appointed or allowed in his word; Matthew 15:9. But in vain do they worship me, teaching for doctrines the commandments of men.
Q. 12. What is the fourth instruction hence? A. Hence we learn how much parents and children are obliged to worship God constantly, spiritually, and agreeably to his will revealed in his word; otherwise the jealousy of God will visit them both in the way of judgment: For as obedience entails a blessing, so disobedience entails a curse on posterity; Exodus 34:14. For thou shalt worship no other god; for the Lord, whose name is Jealous, is a jealous God.