Why did He show unto Moses the fire in the midst of the thorn-bush? || But the fire refers to Israel, who are compared to fire, as it is said, "And the house of Jacob shall be a fire" (Obad. 18). The thorn-bush refers to the nations of the world, who are compared to thorns and thistles. He said to him: Likewise shall Israel be in the midst of the nations. The fire of Israel shall not consume the nations, who are compared to thorns and thistles; but the nations of the world shall extinguish the flames of Israel—(these flames) are the words of the Torah. But in the future that is to come the fire of Israel will consume all the nations, who are compared to thorns and thistles, as it is said, "And the peoples shall be as the burnings of lime" (Isa. 33:12).
Why God Showed Moses Fire in a Thorn Bush
Pirkei DeRabbi Eliezer 40:9