Why Balaam Could Not Curse Israel Whom Isaac Had Blessed

"He couches, he lies down like a lion" (Numbers 24:9). For he shall fall upon all the nations like a lion. After they conquer the Land, no other nations shall come to drive them out of their land. This is the meaning of "like a lioness, who shall rouse him?" "Blessed are those who bless you." Balaam said to him: As for what you say, "neither curse them at all nor bless them at all" (Numbers 23:25), I will not restrain myself from blessing them. For Isaac already blessed Jacob, as it is said, "and blessed be those who bless you" (Genesis 27:29), so that everyone who blesses Israel is himself blessed. And as for what you say to me, "Come, curse Jacob for me," his father Isaac already blessed him, and said, "cursed be those who curse you" (Genesis 27:29), so that everyone who curses Israel shall be cursed. And if I should curse them, I would be among the cursed. Therefore, when Balak heard Balaam say "cursed be those who curse you," at that moment Balak recognized concerning Balaam that if he should curse them, he himself would be among the cursed; and he was afraid to curse them further. Therefore his anger burned, as it is said, "and Balak's anger burned" (Numbers 24:10) — for he no longer had the strength to curse them.