“And Jacob said, “First swear to me”; so he swore to him, and sold his birthright to Jacob. Then Jacob gave Esau bread and lentil stew; and he ate and drank, and rose and went on his way. Thus Esau despised his birthright.”  Gen. 25:33-34

The sale of the birthright is mentioned in legal terminology (Rashi, Plaut), Jacob was not kidding around.  Plaut’s Modern Commentary on the Torah also notes that birthrights in scripture, have not only been sold, as in the case of Esau, but also canceled through blessings as in the case of Manasseh (Gen. 48:13-20), or lost due to a sinful act, like Reuben’s (1 Chron. 5:1).

We often forget that God is God; He can do as He pleases.  His sovereignty goes beyond the natural world we know.  He reaps where He does not sow, He gathers where He did not scatter (Matt. 25:24), and so it should not be that amazing of a thing to us to say he can cause us to no longer be the firstborn.

Likewise, He can cause us to be born again:

“Do not be amazed that I said to you, ‘You must be born again.’ “The wind blows where it wishes and you hear the sound of it, but do not know where it comes from and where it is going; so is everyone who is born of the Spirit.”  (John 3:7-8)

Author R’ Bachya speculates that Esau did not even know for sure what he was selling his birthright for, as it is not revealed to the reader until after the deal is done – that he sold his birthright for a mere pot of beans.  No wonder Esau despised his birthright.

Everett Fox notes Esau’s hasty nature, reinforced by the string of four verbs in the last verse of the chapter – that he ate, drank, arose and went.