Derech Hashem – The Way of G-d 2:4:5
Now, just as all of Adam and Eve’s descendants were originally divided into source “trees” with “branches”, each subsequent “tree” was able to yield its own “branches” which could then produce their own off-springs 1.
Abraham’s “branches” 2 could only number 600,000, which is the number of Jews who left Egypt, received the Torah at Mount Sinai 3, and inherited the Land of Israel 4, who thus comprised the essential Jewish Nation. All Jews who descended from them are considered their “branches” and off-spring.
The other nations were given one more opportunity to achieve their spiritual potential — when the Torah was given to us and they, too, were offered it 5. Had they in fact accepted it, they’d have been given the same spiritual potential as the Jewish people, but they declined it. Their fate was then sealed and the gate 6 was permanently closed 7. Still and all as we said, any individual non-Jew can decide to attach him- or herself onto Abraham’s “tree” 8.
1 Without restriction.
2 On the other hand.
3 Ramchal spoke of the centrality of the revelation at Mount Sinai in a number of his works. See for example Da’at Tevunot 78, 159, Tikkunim Chadashim 21, 33, 42, and Klach PitcheiChochma 30.
4 He also spoke of the centrality of the Land of Israel in several of his works. See for example Adir Bamarom p. 235; also see Ma’amar Hachochma (Tephillat Rosh Hashanah) for the relationship between it and the Jewish Nation.
5 See Avoda Zara 2b.
6 Of access to that special level.
7 See 2:4:2 where it’s said that “humanity has been granted the freedom to choose to ascend to a very great level. It’s just that there’s a time limit within which we can do that”.
8 That’s to say that the Jewish Nation was purposely set up from the start to be a small, “tight” corps of agents of change and rectification which can take on new members but will never be large.