The Rainbow and the Seven Noahide Laws
God makes a covenant with all humanity: the rainbow is the sign that no flood will return, and seven commandments become the law for every human being.
Coming out of the ark, Noach and his sons receive the first covenant in history made not with a nation but with all living things: «I establish My covenant with you and your offspring after you, and with every living soul… never again will there be a flood to destroy the earth.» The sign is the rainbow: «My bow I have set in the cloud, and it shall be a sign of the covenant between Me and the earth.»
With the covenant comes law. Meat is permitted, which it had not been before the Flood — but with the blood forbidden, and with a ban on flesh torn from a living animal. Human life is declared inviolable: «Whoever sheds human blood, by man shall his blood be shed, for in the image of God He made man.» From here the sages derive the seven Noahide laws binding on all humanity: prohibitions of idolatry, blasphemy, murder, sexual immorality, theft and eating flesh from a living animal — and the duty to establish courts.
A non-Jew need not become a Jew to have a share in the World to Come; living by these seven suffices.