The central dramatic incident in Parashat Toldot is the “purloined blessing” described in Beraishit 27. Yitzchak intimates that he wishes to give a special blessing to his son Eisav prior to the patriarch’s death, which sets Rivka in motion to orchestrate a means by which Yaakov can intercept the blessing and obtain it for himself. Although Rivka appears to take the lead in aiding and abetting her preferred son’s subterfuge (Ibid. 27:5-13), an earlier incident involving the twins already demonstrates that Yaakov was interested in supplanting his older brother’s preferred status, even if doing so meant taking advantage of an infirmity and sense of desperation on Eisav’s part:
Ibid. 25:29-34
29 And Yaakov sod pottage; and Eisav came in from the field, and he was faint. 30 And Eisav said to Yaakov: “Let me swallow, I pray thee, some of this red, red (pottage); for I am faint.” Therefore was his name called Edom. 31 And Yaakov said: “Sell me first thy birthright.” 32 And Eisav said: “Behold, I am at the point to die; and what profit shall the birthright do to me?” 33 And Yaakov said: “Swear to me first;” and he swore unto him; and he sold his birthright unto Yaakov. 34 And Yaakov gave him bread and pottage of lentils; and he did eat and drink, and rose up, and went his way. So Eisav despised his birthright.