What did Yitzchak mean when he blessed Esav, "Kasher Tarid u'Farakta Ulo"?
Rashi, Targum Onkelos and Targum Yonasan: When Yaakov fails to observe the Torah, you will cast off his yoke. 1
Ramban, Rashbam and Seforno: When Yaakov is too harsh on you, you will cast off his yoke. 2
Da'as Zekenim: When you will willingly serve Yaakov, you will cast off his yoke, that he cannot subjugate you too much.
Ohr ha'Chayim #1: All Esav's Berachos are for would he serve Yaakov, or he is subjugated under him. He will cast off his yoke, but then Beis Yaakov will be a flame [that will consume Esav - Ovadyah 1:18). This is why it says "v'Hayah," an expression of Simchah, for then Shamayim and Aretz will rejoice.
Ohr ha'Chayim #3: When you will rule in the world, 3 you will cast off his yoke, but neither of you will rule over the other.
This is similar to the prophecy during Rivkah's pregnancy, according to Targum Yonasan (Refer to 25:23:3:1).
Ha'amek Davar: The nation called Edom will never be a mighty kingdom, just individuals from Edom will rule over nations, e.g. Caesars of Rome came from Tzefo ben Elifaz. Through them, Edom will leave the yoke of Yaakov.
QUESTIONS ON RASHI
Rashi writes: "'When you will be pained' - When Bnei Yisrael transgress the Torah...." How do we know that Esav's claim due to his pain is only valid when the Bnei Yisrael sin?
Gur Aryeh #1: A person only feels pained upon seeing someone else more successful, if he feels that that person does not deserve it, such as a Rasha. (As long as Bnei Yisrael keep the Torah, Esav must admit that they are deserving!)
Gur Aryeh #2: If Esav could remove his yoke any time he felt pained, the blessings Yaakov had received would never take effect! 1
Therefore, we must say that this caveat refers to specific circumstances only, i.e. when Bnei Yisrael do not keep the Torah.