Derech Hashem – The Way of G-d 2:4:7
Righteous non-Jews also earn a place in the world to come1. But their experience there would be unlike our own 2.
They’ll serve a supplementary and subservient role there, though, like clothing to a body 3. As that is all they could ever hope for, given the phenomena we’d cited above 4.
1 See Sanhedrin 105a, Hilchot Teshuva 3:3; though also see Zohar Chadash 78d and T.Y. Berachot 9a.
A “righteous gentile” is defined classically as a non-Jew who accepts the seven Noachite Mitzvahs (see 2:4:6) with certain conditions (see Hilchot Malchim 8:11). In any event, this underscores the idea that an individual can be judged for his own actions, rather than one of a multitude of descendants of a particular “branch”.
2 Thanks to the merits of our ancestors and to the eternal covenant that G-d and we entered into. See more about this in Avodat Hakodesh 2:41, Reishit Chochma “Yirah” 13, and in a number of other traditional sources.
3 This arresting image can either be off-putting (a piece of clothing rather a full human being) or perhaps even flattering (along the lines of “clothing makes the man”), but Ramchal has a wholly unexpected take on it in Adir Bamarom. He speaks there (p. 609) of humankind having been born with souls and clothing at first, and that the latter had to be removed once Adam and Eve sinned and to be “converted” (i.e., returned to their native purity by becoming a part of the Jewish Nation), which would ultimately happen (see p. 353 there) and be the ultimate act of rectification.
4 That is, given our people’s role in the wake of Adam and Eve’s sin and in the course of G-d’s intentions for humanity.