'Birthright' in the Bible

Jacob replied, “First sell me your birthright.”

“Look,” said Esau, “I’m about to die, so what good is a birthright to me?”

Jacob said, “Swear to me first.” So he swore to Jacob and sold his birthright to him.

Then Jacob gave bread and lentil stew to Esau; he ate, drank, got up, and went away. So Esau despised his birthright.

So he said, “Isn’t he rightly named Jacob? For he has cheated me twice now. He took my birthright, and look, now he has taken my blessing.” Then he asked, “Haven’t you saved a blessing for me?”