Then Jacob said, "Swear to me as of this day." So he swore to him, and sold his birthright to Jacob.
Genesis 25:33
Surrounding context
25:32 And Esau said, "Look, I am about to die; so what is this birthright to me?"
25:33 Then Jacob said, "Swear to me as of this day." So he swore to him, and sold his birthright to Jacob.
25:34 And Jacob gave Esau bread and stew of lentils; then he ate and drank, arose, and went his way. Thus Esau despised his birthright.