This chapter also deals with a number of mitzvot that share a common theme and are derived from a single Biblical passage. Deuteronomy 13:2-12 relates:
[This is what you must do] when a prophet... arises and presents you with a sign or miracle... and says to you, "Let us follow after other gods whom you do not know and worship them." Do not listen to the words of that prophet.... That prophet... shall die, because he spoke rebelliously against God, your Lord....
[This is what you must do] if your brother..., your son, your daughter, your bosom wife, or your closest friend secretly proselytizes among you, and says, "Let us go and worship other gods whom neither you or your ancestors know."... Do not be attracted to him or listen to him. Do not let your eyes pity him. Do not show him any compassion. Do not try to cover up for him. Rather, you must surely put him to death. Your hand must be the first against him to kill him.... Stone him to death... because he tried to sway you away from God, your Lord.... And all Israel will hear and they will become afraid and they will not continue to do such evil things.
In Sefer HaMitzvot, the Rambam cites six mitzvot which are derived from this passage:
Negative Commandment 16: Not to persuade a single individual to worship [a false deity];
Negative Commandment 17: Not to love a mesit (one who proselytizes on behalf of a false deity);
Negative Commandment 18: Not to reduce one's hatred for him;
Negative Commandment 19: Not to save his life;
Negative Commandment 20: Not to advance any arguments on his behalf;
Negative Commandment 21: Not to withhold information that will lead to his conviction;
A person who proselytizes [a mesit] to any single Jew [a musat] - whether man or woman - on behalf of false deities should be stoned to death. [This applies] even if neither the mesit or the musat actually worshiped the false deity.
As long as he instructed him to worship [the false deity], he should be executed by stoning, regardless of whether the mesit was a prophet or an ordinary person, or whether the musat was a single individual - man or woman - or whether several people were proselytized.
A person who proselytizes the majority of the inhabitants of a city is called a madiach rather than a mesit. If the person who leads the majority of a city astray is a prophet, he is executed by stoning, and the people who were led astray are judged as individuals, and are not considered to be inhabitants of an עיר הנדחת. [For the latter laws to be applied,] two people must proselytize them.
If a person says: "A false deity told me: 'Serve me,'" or "The Holy One, blessed be He, told me: 'Serve a false deity'" - he is considered a prophet who leads others astray. If the majority of the city's inhabitants are swayed by his words, he should be stoned to death.
A mesit should be stoned to death whether he proselytizes in plural terms or in singular. What is implied? He is considered a mesit if he tells a colleague, "I will worship a false deity. [Follow me.] I will go and worship..." or "Let us go and worship following the particular rite with which that deity is served," "I will slaughter. [Follow me.] I will go and slaughter..." or "Let us go and slaughter," "I will bring a burnt offering. [Follow me.] I will go and bring a burnt offering..." or "Let us go and bring a burnt offering," "I will offer a libation. [Follow me.] I will go and offer a libation..." or "Let us go and offer a libation," or "I will bow down. [Follow me.] I will go and bow down..." or "Let us go and bow down."
When a person proselytizes two individuals, they may serve as witnesses against him. They should summon him to court and testify against him, relating what he told them, and the mesit is stoned.
A mesit does not need a warning.
If one proselytizes a single individual, the latter should tell him, "I have friends who would also be interested in this," and thus he should lure him into proselytizing before two people, so that the mesit can be executed.
If the mesit refuses to proselytize before two people, it is a mitzvah to set a trap for him. A trap is never set for a person who violates any of the Torah's other prohibitions. This is the only exception.
How is the trap set for him? The musat should bring two people and place them in a dark place where they can see the mesit and hear what he is saying without his seeing them. He tells the mesit: "Repeat what you told me privately."
[When] he does so, the musat should reply: "How can we forsake our God in heaven and serve wood and stone?" If [the mesit] retracts or remains silent, he is not held liable. If he tells him, "This is our obligation and this is beneficial to us," those who stand far off have him summoned to court and stoned.
It is a mitzvah for the musat to kill [the mesit], as [Deuteronomy 13:10] states: "Your hand must be the first against him to kill him."
It is forbidden for the musat to love the mesit, as [the previous verse states]: "Do not be attracted to him." Since [Exodus 23:5] states with regard to an enemy: "You must surely help him," [the question arises:] Perhaps you should help a mesit? The Torah [Deuteronomy, ibid.] teaches, "Do not... listen to him."
Since [Leviticus 19:16] teaches: "Do not stand idly over your brother's blood," [the question arises:] Perhaps you should not stand idly over a mesit's blood? The Torah teaches, [Deuteronomy, ibid.] "Do not let your eyes pity him."
The musat is forbidden to advance any arguments on his behalf, as [the verse continues,] "Do not show him any compassion." If he knows incriminating evidence, he is not permitted to remain silent, as [the verse continues,] "Do not try to cover up for him."
What is the verse which serves as a warning against a common person proselytizing as a mesit? "And all Israel will hear and they will become afraid [and they will not continue to do such evil things]" (Deuteronomy 13:12).
[The following rules apply to] a person who proselytizes others by telling them to worship him: Should he tell them: "Worship me," and they worship him, he should be stoned. If they did not worship him, even though they accepted and agreed to his statements, he is not liable for stoning.
In contrast, if he proselytizes by telling them to worship another man or another false deity, [different rules apply:] If they accept his statements and say, "We will go and worship," even if they have not actually worshiped, both of them - the mesit and the musat - should be stoned. [Deuteronomy 13:9] states: "Do not be attracted to him or listen to him." Thus, if one was attracted and listened, one is held liable.
What is meant by [the expression,] a prophet who prophesies in the name of false gods? A person who says: "This false deity or this star told me that we are commanded to do such and such or to refrain from doing so." [This applies] even when he stated the law accurately, labeling the impure as impure and the pure as pure.
If a warning was given to him [beforehand], he is executed by strangulation, as [Deuteronomy 18:20] states: "And one who speaks in the name of other gods, that prophet shall die." The warning against this [transgression] is included in the statement, [Exodus 23:13:] "And you shall not mention the name of other gods."
It is forbidden to enter into a discussion or a debate with one who prophesies in the name of a false deity. We may not ask him to perform a sign or wonder, and if he does so on his own accord, we should pay no attention to it nor think about it.Whoever contemplates about the wonders [he performed, thinking], "Perhaps they are true," violates a negative commandment, as [Deuteronomy 13:4] states: "Do not listen to the words of that prophet."
Similarly, a false prophet should be executed by strangulation. [He is to be executed] although he speaks in the name of God and neither adds to nor diminishes [the mitzvot], as [Deuteronomy 18:20] states: "However, the prophet who dares to speak a matter in My name which I did not command - that prophet shall die."
[The category of] a false prophet includes:
a) one who "prophesies" regarding something that was never heard through prophetic vision;
b) one who "prophesies" about a subject which he heard from another prophet, saying that this prophecy was given to him.
[Both of these individuals] are to be executed by strangulation.
Anyone who refrains from executing a false prophet because of the latter's [spiritual] level, [as expressed by] his adherence to the paths of prophecy, violates a negative commandment, as [Deuteronomy 18:22] states: "Do not fear him." Similarly, included within [the scope of the prohibition:] "Do not fear him" are one who withholds incriminating testimony against [a false prophet] and one who is afraid or in awe of his words.
A false prophet may be tried only by the [supreme] court of 71 judges.
A person who makes a vow or takes an oath in the name of a false deity is [liable for] lashes, as [Exodus 23:13] states: "And you shall not mention the name of other gods."
[This applies] both to one who takes such an oath for his own reasons and to one who takes such an oath because of a gentile. It is forbidden to have a gentile take an oath on his deity. It is even forbidden to mention the name of a gentile deity without any connection to an oath, as [implied by the expression], "You shall not mention."
A person should not tell a colleague: "Wait for me near a particular false deity," or the like.
It is permitted to mention the name of any false deity that is mentioned in the Bible - e.g., Peor, Ba'al, Nevo, Gad, and the like. It is forbidden to cause others to take oaths or vows in the name of false deities. [In regard to all these prohibitions,] the only [transgressor] liable for lashes is one who [himself] makes a vow or an oath in the name [of a false deity].