Commentary for Genesis 27:13

עלי קללתך, upon me and my neck; she was relying on the prophecy she had received during her pregnancy that the older son would serve the younger one (25,23)

עלי קללתך, I will take your curse in your place should you become the subject of a curse. We find in Sanhedrin 48, that Solomon is reported to have accepted for himself any curse which would devolve upon him for carrying out his father’s dying wish not to let Yoav die a peaceful death and David’s curses against Yoav. In the event, Solomon or his descendants were afflicted with these curses. [I presume the author just wished to authenticate that Rivkah’s statement was not spurious, and that one can substitute oneself for the target of curses pronounced on someone else. Ed.]

עלי קללתך בני, "may your curse be on me my son!" The reason that she added the word "my son," although she had been talking to him all the time was that she referred only to what Jacob had said last. We have a rule in Makkot 11 that the curse of a Torah scholar, even if uttered only conditionally, is effective. Had Rebeccah not added the word "my son," we would have thought that she referred to Jacob's being cursed by Isaac when he found out he had been tricked.