Genesis 25:31-35

But Jacob said, “First sell me your birthright.”

Esau said, “Look, I am about to die; so of what use then is the birthright to me?”

And Jacob said, “First swear to me”; so he swore an oath to him, and sold his birthright to Jacob.

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