‘And he said, “Is he not rightly called Jacob? For he has supplanted me these two times. He took away my birthright, and see, now he has taken away my blessing.”
Esau makes a bitter play on words. The root idea behind the word ‘Jacob' is protection. Jacob-el (the el is assumed) means ‘may God protect'. But a secondary root which indicates supplanting can also be read into the consonants (see on Genesis 25:26).
Esau claims to see birthright and blessing as two separate things, but had he thought it through he would have recognised that he was wrong. For as the wording of Isaac's blessing made abundantly clear, in the firstborn's case they are really two parts of the one privilege. While it is true that the birthright centred more on property and official position over the tribe, and the blessing concentrated more on the giving of something personal, in the case of the firstborn both were interconnected.
The blessing was specially directed in the light of the birthright. Had Esau received the blessing and yet yielded to Jacob the birthright both would have been in an impossible position. And Esau would probably have won, because the blessing would have been seen as empowering him in a way the birthright did not. If Esau did not see the implications behind the situation there can be no doubt that Jacob and Rebekah did.
There is therefore poetic justice in the fact that Esau, who was seeking to supplant his brother in spite of his oath, finds himself supplanted. Later he would in fact recognise the justice of it and be reconciled with his brother.