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Sanhedrin 37a explains (excerpt from Sefaria):
Therefore, Adam the first man was created alone, to teach you that with regard to anyone who destroys one soul from the Jewish people, i.e., kills one Jew, the verse ascribes him blame as if he destroyed an entire world, as Adam was one person, from whom the population of an entire world came forth.
Murder is a Noahide prohibition. Why, then, does the Gemarah say "...the Jewish people" instead of generalizing it?