In the New King James Version it sounds as though verses 39 and 40 are a blessing from Isaac. They are not! It is a prophecy. It is not a blessing! He just said that he did not have anything left to give him. The blessing was an "all or nothing" portion of an inheritance. Verse 39 has been poorly translated:
There will be continual strife between Jacob and Esau. Jacob would, more often than not, be in charge—until Esau would rebel in frustration and anger. There would be a constant, brotherly quarrel. They would frequently come to blows. This gives us an idea of the mindset of the Edomites. Everything that should have been theirs was now Jacob's and they would fight until the end of days to get it back!
But God says it was not to be. Every once in a while Esau might get the upper hand, but Jacob would have the birthright and the blessing and they would be the ones who would ultimately prevail.
