What did Rivkah mean when she said "Alai Kilelascha Beni"?
Targum Yonasan and Seforno: "If he will bless you then you and your children will be blessed, whereas if he curses you, then they will come upon me!" 1
Divrei Eliyahu and Kol Eliyahu (42:36): I know through Nevu'ah that your curses (great afflictions) will be "Alai' (an acronym for Esav, Lavan, Yosef). No additional curse will come from this (refer to 42:36:151:2). This is why she did not say 'he will not curse you'!
Ohr ha'Chayim: Just now, you mentioned a curse on yourself. A Chacham's curse is fulfilled, even if it was conditional and the Tenai was not fulfilled! I caused this; I accept the result on myself. "Beni" clarifies that she does not discuss a curse that Yitzchak might give.
Malbim: If he will want to curse you, tell him that I commanded you to do so, and his anger will be at me. He will know that you did not do so amidst desire for this world, only because I commanded you. He will not curse you, especially since there was the prophecy "v'Rav Ya'avod Tza'ir" (25:23). You bought the Bechorah, but this does not make you the 'Rav' that must serve the younger. For this, Esav is still the older.
Like we find with Shlomo ha'Melech, who took upon himself the curses of Yo'av, which later materialized, as recorded in Sanhedrin 48b; or, because Yaakov did what he did at her behest. (EC).
Ha'Kesav veha'Kabalah: Mechilta of R. Shimon says that the Shechinah told her that Yitzchak commanded Esav - 'Ani Metzavah Osach' (27:8) refers to the Shechinah. This combined with the prophecy of Shem, "v'Rav Ya'avod Tza'ir" (25:23).
Ha'Kesav veha'Kabalah: Alai refers to removal. I have no concern lest he curse you.