It is forbidden to worship any created thing. Even if the worshipper knows that Ha-Shem is G-d, and he is worshipping this created thing because he believes that G-d wants it to be honored, he is still regarded as an idolator. This is what the Torah warned against: "And lest you lift up your eyes to the heavens and see the sun and the moon and the stars, all the host of heaven that Ha-Shem your G-d apportioned to all the nations, and you are drawn away and bow down to them and worship them"¹ -- that is, lest you think that these are the leaders which G-d gave to the world and it is therefore proper to bow down to them and worship them. And on the same subject He commanded "Take care lest your hearts be deceived [and you turn away and worship other gods and bow down to them]"² -- that is, lest you err in your hearts and worship these as intermediaries between yourselves and the Creator.^a The commandment against idolatry is as important as all the other commandments combined. A person who accepts idolatry denies all of the Torah and the prophets. A Jew who becomes an idolator is like a non-Jew in all respects.^b

It is forbidden to worship an idol in the way it is customarily worshipped, as it says "And you shall not worship them".³ It is also forbidden to sacrifice to it or to bow down to it even if it is not customarily worshipped in these ways, as it says "One who sacrifices to a god, except to Ha-Shem only, shall be destroyed"⁴; and it says "You shall not bow down to them"³ and "You shall not bow down to another god".^5,c It is forbidden to make an idol, as it says "You shall not make yourselves metal gods",⁶ or to have one made for oneself, as it says "You shall not make yourself an idol or any image".^7,d It is also forbidden to make raised figures of men or of heavenly bodies even for decoration, as it says "You shall not make [gods of silver or gods of gold] with Me".^8,e

It is forbidden even to look at idols or to study how they are worshipped, as it says "Do not turn toward idols",⁶ and it says "And lest you inquire after their gods, saying `How do these nations worship their gods'"⁹; for this can lead you to do as they do, as it says "that I too may do so".^9,f It is forbidden to turn toward idolatry even in one's mind; we are warned against all thoughts that might lead to the uprooting of any of the basic principles of the Torah, as it says "And you shall not wander after your hearts or after your eyes which you are used to straying after".^10,g

A person who accepts idolatry as true, even if he has not worshipped, blasphemes against Ha-Shem, as it says "And the person who acts high-handedly... is blaspheming against Ha-Shem".^11,h Blasphemy itself is also forbidden, as it says "You shall not curse G-d",¹² and it says "One who blasphemes the name of Ha-Shem shall be put to death".^13,i It is forbidden to mention the name of idolatry or to swear by it, as it says "And you shall not mention the name of another god".^14,j

We are commanded to destroy idols and everything used in their worship, as it says "You shall destroy all the places where the nations... worshipped their gods... and you shall break down their altars and smash their pillars and burn their sacred trees and chop down their idols and destroy their name out of that place".¹⁵ "Thus shall you do to them: break down their altars, smash their pillars, chop down their sacred trees, and burn their idols".^16,k It is forbidden to derive benefit from any of these things, as it says "And you shall not bring an abomination into your house",¹⁷ and it says "You shall burn the idols of their gods in fire; you shall not covet the silver and gold on them and take it for yourself".^18,l

b) Incitement to Idolatry

A Jew who incites others to idolatry must be mercilessly punished, as it says "[If your brother... entice you, saying `Let us go and worship other gods'...] you shall not consent and you shall not listen to him and you shall not pity him and you shall not have mercy on him or conceal him; your hand shall be the first to put him to death... and all Israel shall hear and see and cease to do such a thing among you".<sup>19,m</sup> If the majority of the inhabitants of a Jewish city are incited to idolatry the city must be destroyed, as it says "If you hear... that evil men have incited the inhabitants of their city, saying `Let us go and worship other gods'... you shall smite the inhabitants of that city with the sword, destroy it and all that is in it... and you shall burn the city and all its booty... it shall not be built again and none of the [booty] shall remain in your hands...".^20,n

It is forbidden to prophesy in the name of idolatry or to prophesy falsely even in G-d's name, and it is forbidden to listen to such a prophet, as it says "But the prophet who presumes to say something in My name that I did not command him to say or who speaks in the name of other gods, that prophet shall die... you shall not fear him",²¹ and it says "If a prophet arises among you...saying `Let us go after other gods'... you shall not listen to the words of that prophet".^22,o

Contact with idolators should be avoided if it is likely to support them in idolatry ^p and certainly if there is any danger of them leading us astray, as it says "You shall not make a treaty with them or show mercy to them",²³ and it says "[You shall make no treaty with them or with their gods;] they shall not dwell in your land lest they cause you to sin against Me, for you will worship their gods",²⁴ and it says "Lest you make a treaty with the dweller[s] in the land and they stray after their gods and sacrifice to their gods and he calls you and you eat from his sacrifice...".^25,q

c) Idolatrous and Magical Practices

It is forbidden to imitate the style of worship used by idolators even in worshipping Ha-Shem. In particular, the Torah forbids erecting pillars for worship, as it says "And you shall not set up a pillar ²⁶; or setting down stones to bow down on except in the Temple, as it says "[You shall not make yourselves false gods nor set up idols or pillars] and you shall not put carved stones in your land to bow down on"²⁷; or planting trees in the Temple, as it says "You shall not plant any sacred tree next to the altar of Ha-Shem your G-d".^28,r

Divination and sorcery are forbidden; the Torah enumerates many specific types: "Do not turn to ghosts or familiar spirits"^29,s; "[You shall not learn to imitate the abominations of those nations;] there shall not be found among you one who passes his son or daughter through fire (this refers to Moloch worship: "You shall not give of your seed to pass to Moloch"^30,t), a diviner, a soothsayer, an enchanter, a sorcerer, a charmer, one who consults a ghost or familiar spirit, or a necromancer"³¹; "You shall not practice divination or soothsaying".^32,u

d) The Customs of the Nations

A Jew should not follow the customs of the nations by imitating them in styles of dress or hair or the like, as it says "And you shall not follow the customs of the nations",³³ and it says "And you shall not follow their customs",³⁴ and it says "Take care lest you are entrapped into following them".³⁵ A Jew should be distinguished from them in his clothing and actions as he is in his thoughts, as it says "And I separated you from the nations to be Mine".^36,v In particular it is forbidden to shave the "corners" of the head or the beard, as it says "You shall not round off the border of your head... or destroy the border of your beard".^37,w A woman should not wear man's clothes or ornaments nor a man women's [as it says "A man's trappings shall not be on a woman nor shall a man wear a woman's garment"].^38,x Tattooing is forbidden, as it says "And you shall not put marks on yourselves".^39,y Cutting oneself or tearing one's hair over the dead is also forbidden, as it says "You shall not make cuts in your flesh for a spirit",³⁹ and it says "You shall not cut yourselves or make baldness between your eyes for the dead".^40,z

Sources:
1. Deut. 4:19	a. 2:1
2. Deut. 11:16	b. 2:4-5
3. Ex. 20:5	c. 3:2-3
4. Ex. 22:19	d. 3:9
5. Ex. 34:14	e. 3:10-11
6. Lev. 19:4	f. 2:2
7. Ex. 20:4	g. 2:3
8. Ex. 20:20	h. 2:6
9. Deut. 12:30	i. 2:7-8
10. Num. 15:39	j. 5:10-11
11. Num. 15:30	k. 7:1
12. Ex. 22:27	l. 7:2; 8:7
13. Lev. 24:16	m. 5:4
14. Ex. 23:13	n. 4:6-7
15. Deut. 12:2-3	o. 5:6-7,9
16. Deut. 7:5	p. 9:8
17. Deut. 7:26	q. 10:1,6; 9:15
18. Deut. 7:25	r. 6:6-9
19. Deut. 13:7-12	s. 6:1-2
20. Deut. 13:13-18	t. 6:3
21. Deut. 18:20,22	u. 11:4,6-10,13-15
22. Deut. 13:2-4	v. 11:1
23. Deut. 7:2	w. 12:1,7
24. Ex. 23:32-33	x. 12:10
25. Ex. 34:15	y. 12:11
26. Deut. 16:22	z. 12:12-13,15
27. Lev. 26:1
28. Deut. 16:21
29. Lev. 19:31
30. Lev. 18:21
31. Deut. 18:9-10
32. Lev. 19:26
33. Lev. 20:23
34. Lev. 18:3
35. Deut. 12:30
36. Lev. 20:26
37. Lev. 19:27
38. Deut. 22:5
39. Lev. 19:28
40. Deut. 14:1