Musar zu Dewarim 10:22

The entire nation is considered as if it were one person; this is why the Torah refers to the people as נפש, person (singular) already at the time Jacob descended into Egypt (Genesis 46,26, et al.). The significance of this lies in the fact that כי חלק ה' עמו, "that His people Israel are part of G–d Himself" (32,9). The remainder of mankind was divided into 70 nations, each one with a representative in the Celestial Regions, i.e. a horoscope presided over by a שר, "Minister," as we know from 4,19: "which the Lord your G–d assigned to all the nations; He took you and removed you from the iron crucible, from Egypt, to be for Him His very own nation, as is now the case" (4,20). The Jewish people's fortunes are not guided by intermediaries such as horoscopes. The 70 nations were divided from one another as we know from 32,8: "When the most High gave nations their homes and set the divisions of man, He fixed the boundaries of peoples in relation to Israel's numbers." The relationship (common denominator) between the "numbers" of Israel and that of the nations of the world is that Israel numbered 70 when they first went down to Egypt. The difference is only that the 70 Israelites that came to Egypt are all described as נפש, a single person. Any part of the Jewish nation is compared to the entire nation. Because Israel is part of G–d, it has an eternal future, as pointed out in Sanhedrin 90a: "Every Israelite has a share in the World to Come."