'Birthright' in the Bible

But Jacob responded, "Sell me your birthright. Do it now."

"Look! I'm about to die," Esau replied. "What good is this birthright to me?"

But Jacob insisted, "Swear it by an oath right now." So he swore an oath to him and sold his birthright to Jacob.

Then Jacob gave Esau some of his food, along with some boiled stew. So Esau ate, drank, got up, and left, after having belittled his own birthright.

Then he said, "Isn't his name rightly called Jacob?" Esau asked. "He has circumvented me this second time. First, he took away my birthright, and now, look how he also stole my blessing." Then he added, "Haven't you reserved a blessing for me?"