Genesis 25:29-33

When Jacob had cooked a stew one day, Esau came in from the field and he was exhausted;

and Esau said to Jacob, “Please let me have a mouthful of that red stuff there, for I am exhausted.” Therefore he was called Edom by name.

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.