So far, we have had Cain and Esau demonstrate to us that the first-born son is not always the best one. The Bible is very carefully starting a pattern, one that we will see continued with Jacob’s many sons. To the Hebrews, it is more important that the person most deserving, the one who works the hardest be the one to inherit, regardless of birth order.
At the same time, however, they’re carefully maintaining this tradition. The narratives provide a rationale for changing the tradition on a case-by-case basis, but with a little more evidence, the idea of primogeniture (things passing to the first-born) is something that will pass from the Hebrew system.
Again, it may seem like Jacob and Rebekah are underhanded, but it shows the importance of intelligence and cunning in safeguarding the family legacy. Esau’s carefree and responsibility-free attitude towards life is not enough. Simply by accepting Jacob’s price demonstrates that he is not fit for inheriting the bulk of Isaac’s property, especially as he doesn’t know the first thing about an agrarian lifestyle.