Genesis 25:29-34 New International Version - UK (NIVUK)
29 Once when Jacob was cooking some stew, Esau came in from the open country, famished. 30 He said to Jacob, ‘Quick, let me have some of that red stew! I’m famished!’ (That is why he was also called Edom.[a])
31 Jacob replied, ‘First sell me your birthright.’
32 ‘Look, I am about to die,’ Esau said. ‘What good is the birthright to me?’
33 But Jacob said, ‘Swear to me first.’ So he swore an oath to him, selling his birthright to Jacob.
34 Then Jacob gave Esau some bread and some lentil stew. He ate and drank, and then got up and left.
So Esau despised his birthright.