A Noahide (or Ben Noach) is a non-Jew who voluntarily takes on the Sheva Mitzvot (Seven Laws of Noah). These individuals are considered the Righteous of the Nations (Ger Toshav).
Non-Jews are not required to convert to Judaism to be considered righteous and have a place in the World to Come. They are however, commanded to believe in the God of Abraham, Isaac, and Jacob and follow the Sheva Mitzvot because they are commanded by God.
And behold, I establish My covenant with you, and with your seed after you; (Genesis 9:9)
Moses only gave the Torah and mitzvot as an inheritance to Israel, as Deuteronomy 33:4 states: ‘The Torah… is the inheritance of the congregation of Jacob,’ and to all those who desire to convert from among the other nations, as Numbers 15:15 states ‘the convert shall be the same as you.’ However, someone who does not desire to accept Torah and mitzvot, should not be forced to. By the same regard, Moses was commanded by the Almighty to compel all the inhabitants of the world to accept the commandments given to Noah’s descendants…. (MT Kings and Wars 8:10)
Anyone who accepts upon himself the fulfillment of these seven mitzvot and is precise in their observance is considered one of ‘the pious among the gentiles’ and will merit a share in the world to come. This applies only when he accepts them and fulfills them because the Holy One, blessed be He, commanded them in the Torah and informed us through Moses, our teacher, that Noah’s descendants had been commanded to fulfill them previously.
However, if he fulfills them out of intellectual conviction, he is not a resident alien, nor of ‘the pious among the gentiles,’ nor of their wise men. (MT Kings and Wars 8:11)
Muslims and non-Trinitarian Christians are considered Noahides because they are monotheists who believe in God and follow the Noahide Laws.
These universal laws were given to Adam and Noah and as such are incumbent upon all humans.
And the Lord God commanded the man, saying,,… (Gensis 2:16)
And God spoke to Noah, saying, (Genesis 8:15)
The Gemara asks: If so, let us say with regard to each and every one of the seven Noahide mitzvot that it was repeated because of an additional matter the Torah teaches, and the descendants of Noah are exempt from them all. The Gemara answers that this is what Rabbi Yosei, son of Rabbi Ḥanina, is saying: After stating a prohibition with regard to the descendants of Noah, why do I need the Torah to then repeat the prohibition itself for the Jewish people? If the only purpose is to teach an additional halakha, it is unnecessary to repeat it in the form of a prohibition, e.g., “You shall not murder…you shall not commit adultery” (Exodus 20:13). Therefore, it is derived from the fact that the entire prohibition is repeated, and not just the new details, that it applies both to Jews and to descendants of Noah. (Sanhedrin 59b:5-6)
There are seven mitzvot directed to Adam and Noah and thus, passed on to all of humanity.
Six precepts were commanded to Adam:
a) the prohibition against worship of false gods;
b) the prohibition against cursing God;
c) the prohibition against murder;
d) the prohibition against incest and adultery;
e) the prohibition against theft;
f) the command to establish laws and courts of justice.
Even though we have received all of these commands from Moses and, furthermore, they are concepts which intellect itself tends to accept, it appears from the Torah’s words that Adam was commanded concerning them.
The prohibition against eating flesh from a living animal was added for Noah, as Genesis 9:4 states: ‘Nevertheless, you may not eat flesh with its life, which is its blood.’ Thus there are seven mitzvot. (MT Kings and War 9:1)
The prohibition against worshiping false gods comes from Genesis 2:16: And the Lord God commanded the man, saying,… This shows that God is the Ruler and Creator and is the only one to be served.
The prohibition against cursing God is explicitly stated in Leviticus 24:16: And he who blasphemes the name of the Lord, shall surely be put to death, and all the congregation shall certainly stone him: both the stranger, and he that is born in the land, when he blasphemes the name of the Lord, shall be put to death. However, Tractate Sanhedrin explains that this prohibition is derived from Genesis 2:16 which states, And the Lord God commanded the man, saying,…
The Sages taught in a baraita with regard to the verse: “Anyone who curses his God shall bear his sin” (Leviticus 24:15), that the verse could have stated: One [ish] who curses his God. Why must the verse state: “Anyone [ish ish]”? It is to include the gentiles, who are prohibited from blessing, i.e., cursing, the name of God, just like Jews are. And they are executed for this transgression by the sword alone, as all death penalties stated with regard to the descendants of Noah are by the sword alone. The Gemara asks: But is this halakha derived from here? Rather, it is derived from there: “And the Lord God commanded the man” (Genesis 2:16), as is stated in a baraita that will soon be quoted at length: “The Lord,” this is referring to the blessing, i.e., cursing, of the name of God. This verse concerns Adam, the first man, and is therefore binding on all of humanity. (Sanhedrin 56a:14)
The prohibition against murder comes from Genesis 9:5: And surely your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man’s brother will I require the life of man.
The prohibition against incest and adultery comes from multiple sources in Genesis.
Genesis 2:24: That is why a man leaves his father and his mother, and cleaves to his wife: and they become one flesh.
Genesis 20:12: And yet indeed she is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife.
Genesis 19:29-36: And it came to pass, when God destroyed the cities of the plain, that God remembered Avraham, and sent Lot out of the midst of the overthrow, when He overthrew the cities in which Lot dwelt. And Lot went up out of Żo῾ar, and dwelt in the mountain, and his two daughters with him; for he feared to dwell in Żo῾ar: and he dwelt in a cave, he and his two daughters. And the firstborn said to the younger, Our father is old, and there is not a man in the earth to come in to us after the manner of all the earth: come, let us make our father drink wine, and we will lie with him, that we may preserve seed of our father. And they made their father drink wine that night: and the firstborn went in, and lay with her father; and he perceived not when she lay down, nor when she arose. And it came to pass on the morrow, that the firstborn said to the younger, Behold, I lay last night with my father: let us make him drink wine this night also; and go thou in, and lie with him, that we may preserve seed of our father. And they made their father drink wine that night also: and the younger arose, and lay with him; and he perceived not when she lay down, nor when she arose. Thus were both the daughters of Lot with child by their father.
Leviticus also includes restrictions for the Nations.
Leviticus 18:3,30: After the doings of the land of Miżrayim, in which you dwelt, shall you not do: and after the doings of the land of Kena῾an, into which I bring you, shall you not do: neither shall you walk in their practices. … Therefore shall you keep my ordinance, that you commit not any one of these abominable customs, which were practised before you, and that you defile not yourselves in them: I am the Lord your God.
The prohibition against theft is found in Genesis.
Genesis 2:16-17: And the Lord God commanded the man, saying, Of every tree of the garden thou mayst freely eat: but of the tree of the knowledge of good and evil, thou shalt not eat of it: for on the day that thou eatest of it thou shalt surely die.
Genesis 21:25: And Avraham reproved Avimelekh because of the well of water, which Avimelekh’s servants had violently taken away.
The command to establish laws and courts of justice are derived from Genesis 9:6: Whoso sheds man’s blood by man shall his blood be shed: for in the image of God made He man. This is seen as a command for judging and penalizing a murderer.
However, these seven mitzvot should really just be seen as seven categories and the bare minimum for the Nations.
“[T]he Noahide Laws are only very basic, and beyond the negative prohibitions, they leave the Noahide with almost nothing to do. But the most important thing to realize is that observance and connection to God do not end with the Noahide Laws. … But God wants us to go far beyond the minimum. We can go infinitely higher – and this is what truly defines us as great human beings.” (Rabbi Dovid Rosenfeld – What Does a Noahide Actually do?)
You will read that Maimonides and the Talmud call for capital punishment for non-Jews who violate the Sheva Mitzvot. However, this is viewed as the maximal punishment and is not carried out except in extraordinary circumstances. However, this is not something that has probably ever happened.
In the Tanach, there are multiple instances speaking of the Ger Toshav, who are non-Jews living among Jews in the Land of Israel, who voluntarily take on the Sheva Mitzvot. The Ger Toshav is a protected person within the Land of Israel – they are treated similarly to the orphan and the widow.
Also thou shalt not oppress a stranger: for you know the heart of a stranger, seeing you were strangers in the land of Miżrayim. (Exodus 23:9)
… he executes the judgment of the fatherless and widow, and loves the stranger, giving him food and raiment. (Deuteronomy 10:18)
When thou hast made an end of tithing all the tithes of thy produce in the third year, which is the year of tithing, and hast given it the Levite, the stranger, the fatherless, and the widow, that they may eat within thy gates, and be replete;… (Deuteronomy 26:12)
The Ger Toshav is treated as equal under the law when living in the Land of Israel.
And if a stranger shall sojourn among you, and will keep the passover to the Lord; according to the ordinance of the passover, and according to its prescribed manner, so shall he do: you shall have one ordinance, both for the stranger, and for him that was born in the land. (Numbers 9:14)
And if a stranger sojourn with you, or whoever may be among you throughout your generations, and will offer an offering made by fire, of a sweet savour to the Lord; as you do, so he shall do. (Numbers 15:14)
And it shall be forgiven all the congregation of the children of Yisra᾽el, and the stranger that sojourns among them; seeing all the people were in ignorance. (Numbers 15:26)
The historicity of Noahides was shown in the Roman Empire.
“Yet, proselytes undoubtedly existed earlier, and ‘Godfearers’ or “half-Jews’ continued even at this time, although without incurring the ‘Jewish tax’ and the benefits that went with it.
Indeed, the most striking innovation which can be dated with some confidence to this period – the second to early third century CE – was a new interest among Jews in defining the role and status (in Jewish eyes) of those gentiles who were perceived as being morally good without having chosen to become Jews. Jewish authors of earlier centuries did refer to gentiles, and it was a commonplace that, at the end of days, gentiles would come to recognize the Jewish God; but, on the position of gentiles in the meantime, little more was said than abomination of the idolatry to which it was assumed that they all subscribed. In the second century CE it seems that his lack of concern about gentiles was challenged.” (Martin Goodman – Judaism in the Roman World: Collected Essays)
During the 12th century, Maimonides also spoke of the Noahide laws and the command from God for all non-Jews to follow these laws. In the 19th century, this work was carried on by Rabbi Elijah Benamozegh. Currently, the most outspoken proponent of the Noahide Laws and the spreading of knowledge about the Noahide Laws is the Chabad Movement and many Noahide communities around the globe.
The Noahide Laws are even mentioned in the Christian scriptures.
And certain men came down from Judea and taught the brethren, “Unless you are circumcised according to the custom of Moses, you cannot be saved.” …that you abstain from things offered to idols, from blood, from things strangled, and from sexualimmorality. If you keep yourselves from these, you will do well. (Acts 15:1,29)
This is not to say that the Noahide Laws are the only laws non-Jews may keep.
“In addition, although a non-Jew is not obligated, he can voluntarily keep most of the commandments of the Torah, although he should have in mind that he is doing so as ‘extra credit’ and not as a regular obligation. There are several exceptions to this – such as Shabbat and holidays, Tefillin, Tallit and Mezuzah. He may also study Torah, although he should study only the parts relevant to him – such as the written Torah, the Seven Laws, and basic matters of belief and ethics.” (Rabbi Dovid Rosenfeld – What Does a Noahide Actually do?)
We should not prevent a Noachide who desires to perform one of the Torah’s mitzvot in order to receive reward from doing so, provided he performs it as required. (MT Kings and Wars 10:10)