The concept of a birthright is important throughout the scriptures. In the old testament birthright determined everything from the portion of your inheritance (Deuteronomy 21:15-17) to judicial and familial position. (II Chronicles 21:3) In Genesis 25:19-34 we are given the account of Jacob and Esau. The passage that is of particular interest to us is found in verses 27 - 34.
And the boys grew: and Esau was a cunning hunter, a man of the field; and Jacob was a plain man, dwelling in tents. And Isaac loved Esau, because he did eat of his venison: but Rebekah loved Jacob. And Jacob sod pottage: and Esau came from the field, and he was faint: And Esau said to Jacob, Feed me, I pray thee, with that same red pottage; for I am faint: therefore was his name called Edom. 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. Genesis 25:27-34