What did Rivkah think was the explanation of the struggling within her?
(25,22) “And the children struggled within her, and she said: If so, why this I?, and she went to inquire of Hashem.”
We can explain this posuk on the level of רמז (allusion), according to that which is written in the gemora in several places, that Shimon HaAmsoni expounded all the occurrences of the word את in the Torah, teaching each time what the word came to include. But when he reached the posuk את ה' אלקיך תירא - “you shall fear Hashem, your G-d”, he ceased to do so, because he would have to explain that it is coming to say that you should fear someone else besides Hashem, and that would imply that there are two supreme authorities, G-d forbid. Until R. Akiva came and expounded that the word את comes to include that one should fear Torah sages.
Now, Rashi explained here in the name of the Midrash, that when Rivkah passed by a place of idolatry, Eisav would struggle to come out, and when she passed the Academies of Shem and Ever, Ya’akov would struggle to come out. And Rivkah did not know that there were two foetuses; she thought that there was only one. If so, it gave a reason to think, G-d forbid, that there were two supreme authorities, since there was only one foetus, and yet it displayed two opposite extremes of behaviour. When this thought occurred to her, she said: If so, למה זה אנכי - why this I. That is, why is it written in the ten commandments אנכי ה' אלקיך, that there is only one G-d, when it is in contrast to this struggling within her. Therefore, she went to 'לדרוש את ה, that is, to expound the posuk את ה' אלקיך תירא, that maybe the word את does indeed come to include another authority besides Hashem. But “Hashem said to her: There are two nations in your womb, and two kingdoms will separate from your innards”, and one is righteous and one is wicked. So don’t think, G-d forbid, that there are two supreme authorities.
From where did Chazal learn that Avrohom observed the mitzvah of Eiruv Tavshilin?
(26,5) “Because (עקב) Avrohom hearkened to My voice, and kept My charge, My commandments, My statutes, and My instructions.”
From this posuk Chazal taught in the gemora Yoma 28b that Avrohom observed even ערובי תבשילין (something which needs to be done in order to permit cooking on Yom Tov for the sake of Shabbos). But at first glance this is very astonishing - where does this posuk allude to Eiruvei Tavshilin?!
But it is possible to explain that the text in the gemora is incorrect, and that the correct text should be ערובי תחומין (something which needs to be done to allow a person to walk beyond the two thousand cubit limit on Shabbos). [This is in fact the text which the Rashba brings in his responsa, Siman 94]. And this mitzvah can certainly be alluded to by the word עקב (which also means a heel), because by making Eiruvei Techumin, a person is able to tread with his heel outside of the two thousand cubits on Shabbos.
But a later copyist wrote the two words as just two letters ע"ת, and an even later copyist erred in his understanding of these two letters, and thought that they stood for ערובי תבשילין, and wrote this out in full, and thus this is the incorrect text that we have.