Why does Satan constantly attack the nation of Israel?
Satan constantly attacks the nation of Israel because God's redemptive plan for the ages comes through the Abrahamic covenant and the Messiah, who would descend from Abraham. Satan must do anything in his power to thwart that plan, and he has to start by attacking Israel, the nation through whom the Messiah would come.
Les teaches that God made an Abrahamic covenant with one man, Abraham, and through that covenant comes the Messiah, the Redeemer of all mankind. Because Satan wants to thwart God's plan for the ages, he constantly attacks the little nation of Israel; he has to start with Israel. The surrounding passage shows Abraham questioning how a nation could come when he had no son, with Eliezer and Lot not meeting the criteria, underscoring why the covenant promise and Israel are central to God's purpose.
Who are Israelites; to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises;