Esau said, “Is he not rightly named Jacob? For he has supplanted me these two times. He took away my birthright, and behold, now he has taken away my blessing.” And he said, “Have you not reserved a blessing for me?”
Now the sons of Reuben the firstborn of Israel (for he was the firstborn, but since he defiled his father’s bed, his birthright was given to the sons of Joseph the son of Israel, so that the genealogy is not listed according to the birthright;
then it must be, when he gives his sons the inheritance which he has, that he may not make the firstborn son of the loved come before the son of the unloved, who was indeed the firstborn.
On the contrary, he must acknowledge the son of the unloved for the firstborn, by giving him a double portion of all that he has, for he is the beginning of his strength. The right of the firstborn is his.