The Midrash on Parshat Toldot states that the day that Esav gave away his Bechorah was the day that Avraham died. We know this because Yaakov cooked lentils, and eating lentils is a sign of mourning. One can ask a question regarding Esav’s request to Yaakov: In Perek 25, Pasuk 30, the Torah says, “Vayomer Esav El Yaakov, Hal’iteini Na Min Haadom Haadom Hazeh,” “Esav said to Yaakov, ‘Please give me from this red, red substance.’” Why doesn’t Esav mention the lentils by name, instead of saying “Haadom Haadom Hazeh”?
The Beit Halevi answers that Esav ate the lentils because he was hungry, not because he was a mourner. Once people would see he that was eating the lentils, they would think he was a mourner. Since it would be uncomfortable for him not to be mourning when everyone else was, he had to cover up that he was eating lentils. For this reason he pretended to not know that he was eating lentils, so he called it “Haadom Haadom Hazeh.” This is also the reason he said “Haliteini” – he wanted Yaakov to put the lentils directly into his mouth, so that no one would see that he was eating lentils. As proof of this, Esav said “Ki Ayef Anochi,” expressing that he was tired and therefore did not want to pick up the spoon and eat it himself. Rather, he wanted to have Yaakov pour it directly into his mouth. Thus, Esav was not only showing greed, but was also trying to save his self-image.