Musar zu Dewarim 1:44

As a result, a person who separates himself from the community, pursuing a lifestyle not acceptable to it, divorces himself from life. As a limb detached from its body he will die. This is the meaning of the imposition of חרם, a ban, or excommunication. Such a person is on the way to Chormah, annihilation, (cf. Deut. 1, 44). This is why the numerical value of the word 248=חרם. Israel's essential advantage over the other nations is that it is a composite unit. Our sages have underlined this when they formulated the Shabbat Minchah prayer in which they emphasized that just as G–d is unique in being One, so Israel is unique in being one single unit as a people.