'Birthright' in the Bible

And Jacob said, Sell me this day thy birthright.

And Esau said, Behold, I am at the point to die: and what profit shall this birthright do to me?

And Jacob said, Swear to me this day; and he sware unto him: and he sold his birthright unto Jacob.

Then Jacob gave Esau bread and pottage of lentiles; and he did eat and drink, and rose up, and went his way: thus Esau despised his birthright.

And he said, Is not he rightly named Jacob? for he hath supplanted me these two times: he took away my birthright; and, behold, now he hath taken away my blessing. And he said, Hast thou not reserved a blessing for me?

And they sat before him, the firstborn according to his birthright, and the youngest according to his youth: and the men marvelled one at another.